diff --git a/examples/wifi_loopback.grc b/examples/wifi_loopback.grc
index c95b6f8..90b3bfc 100644
--- a/examples/wifi_loopback.grc
+++ b/examples/wifi_loopback.grc
@@ -1,5 +1,5 @@
 <?xml version='1.0' encoding='ASCII'?>
-<?grc format='1' created='3.8.git'?>
+<?grc format='1' created='3.7.7'?>
 <flow_graph>
   <timestamp>Sat Feb  1 18:28:19 2014</timestamp>
   <block>
@@ -65,6 +65,33 @@
       <value>0</value>
     </param>
   </block>
+  <block>
+    <key>variable</key>
+    <param>
+      <key>id</key>
+      <value>variable_0</value>
+    </param>
+    <param>
+      <key>_enabled</key>
+      <value>True</value>
+    </param>
+    <param>
+      <key>value</key>
+      <value>0</value>
+    </param>
+    <param>
+      <key>alias</key>
+      <value></value>
+    </param>
+    <param>
+      <key>_coordinate</key>
+      <value>(952, 384)</value>
+    </param>
+    <param>
+      <key>_rotation</key>
+      <value>0</value>
+    </param>
+  </block>
   <block>
     <key>variable</key>
     <param>
@@ -92,6 +119,33 @@
       <value>0</value>
     </param>
   </block>
+  <block>
+    <key>variable</key>
+    <param>
+      <key>id</key>
+      <value>out_buf_size</value>
+    </param>
+    <param>
+      <key>_enabled</key>
+      <value>True</value>
+    </param>
+    <param>
+      <key>value</key>
+      <value>96000</value>
+    </param>
+    <param>
+      <key>alias</key>
+      <value></value>
+    </param>
+    <param>
+      <key>_coordinate</key>
+      <value>(1136, 147)</value>
+    </param>
+    <param>
+      <key>_rotation</key>
+      <value>0</value>
+    </param>
+  </block>
   <block>
     <key>variable_chooser</key>
     <param>
@@ -233,65 +287,6 @@
       <value>0</value>
     </param>
   </block>
-  <block>
-    <key>variable_slider</key>
-    <param>
-      <key>id</key>
-      <value>freq_offset</value>
-    </param>
-    <param>
-      <key>_enabled</key>
-      <value>True</value>
-    </param>
-    <param>
-      <key>label</key>
-      <value></value>
-    </param>
-    <param>
-      <key>value</key>
-      <value>0</value>
-    </param>
-    <param>
-      <key>min</key>
-      <value>-10000</value>
-    </param>
-    <param>
-      <key>max</key>
-      <value>10000</value>
-    </param>
-    <param>
-      <key>num_steps</key>
-      <value>1000</value>
-    </param>
-    <param>
-      <key>style</key>
-      <value>wx.SL_HORIZONTAL</value>
-    </param>
-    <param>
-      <key>converver</key>
-      <value>float_converter</value>
-    </param>
-    <param>
-      <key>grid_pos</key>
-      <value></value>
-    </param>
-    <param>
-      <key>notebook</key>
-      <value></value>
-    </param>
-    <param>
-      <key>alias</key>
-      <value></value>
-    </param>
-    <param>
-      <key>_coordinate</key>
-      <value>(947, 7)</value>
-    </param>
-    <param>
-      <key>_rotation</key>
-      <value>0</value>
-    </param>
-  </block>
   <block>
     <key>blocks_add_xx</key>
     <param>
@@ -378,96 +373,6 @@
       <value>180</value>
     </param>
   </block>
-  <block>
-    <key>ieee802_11_ofdm_mac</key>
-    <param>
-      <key>id</key>
-      <value>ieee802_11_ofdm_mac_0</value>
-    </param>
-    <param>
-      <key>_enabled</key>
-      <value>True</value>
-    </param>
-    <param>
-      <key>src_mac</key>
-      <value>[0x23, 0x23, 0x23, 0x23, 0x23, 0x23]</value>
-    </param>
-    <param>
-      <key>dst_mac</key>
-      <value>[0x42, 0x42, 0x42, 0x42, 0x42, 0x42]</value>
-    </param>
-    <param>
-      <key>bss_mac</key>
-      <value>[0xff, 0xff, 0xff, 0xff, 0xff, 0xff]</value>
-    </param>
-    <param>
-      <key>alias</key>
-      <value></value>
-    </param>
-    <param>
-      <key>affinity</key>
-      <value></value>
-    </param>
-    <param>
-      <key>minoutbuf</key>
-      <value>0</value>
-    </param>
-    <param>
-      <key>maxoutbuf</key>
-      <value>0</value>
-    </param>
-    <param>
-      <key>_coordinate</key>
-      <value>(376, 139)</value>
-    </param>
-    <param>
-      <key>_rotation</key>
-      <value>0</value>
-    </param>
-  </block>
-  <block>
-    <key>blocks_message_strobe</key>
-    <param>
-      <key>id</key>
-      <value>blocks_message_strobe_0</value>
-    </param>
-    <param>
-      <key>_enabled</key>
-      <value>True</value>
-    </param>
-    <param>
-      <key>msg</key>
-      <value>pmt.intern("Hello World!")</value>
-    </param>
-    <param>
-      <key>period</key>
-      <value>300</value>
-    </param>
-    <param>
-      <key>alias</key>
-      <value></value>
-    </param>
-    <param>
-      <key>affinity</key>
-      <value></value>
-    </param>
-    <param>
-      <key>minoutbuf</key>
-      <value>0</value>
-    </param>
-    <param>
-      <key>maxoutbuf</key>
-      <value>0</value>
-    </param>
-    <param>
-      <key>_coordinate</key>
-      <value>(96, 131)</value>
-    </param>
-    <param>
-      <key>_rotation</key>
-      <value>0</value>
-    </param>
-  </block>
   <block>
     <key>ieee802_11_ofdm_parse_mac</key>
     <param>
@@ -503,96 +408,6 @@
       <value>180</value>
     </param>
   </block>
-  <block>
-    <key>foo_wireshark_connector</key>
-    <param>
-      <key>id</key>
-      <value>foo_wireshark_connector_0</value>
-    </param>
-    <param>
-      <key>_enabled</key>
-      <value>False</value>
-    </param>
-    <param>
-      <key>tech</key>
-      <value>127</value>
-    </param>
-    <param>
-      <key>debug</key>
-      <value>False</value>
-    </param>
-    <param>
-      <key>alias</key>
-      <value></value>
-    </param>
-    <param>
-      <key>affinity</key>
-      <value></value>
-    </param>
-    <param>
-      <key>minoutbuf</key>
-      <value>0</value>
-    </param>
-    <param>
-      <key>maxoutbuf</key>
-      <value>0</value>
-    </param>
-    <param>
-      <key>_coordinate</key>
-      <value>(632, 163)</value>
-    </param>
-    <param>
-      <key>_rotation</key>
-      <value>0</value>
-    </param>
-  </block>
-  <block>
-    <key>blocks_file_sink</key>
-    <param>
-      <key>id</key>
-      <value>blocks_file_sink_0</value>
-    </param>
-    <param>
-      <key>_enabled</key>
-      <value>False</value>
-    </param>
-    <param>
-      <key>file</key>
-      <value>/tmp/ofdm.bin</value>
-    </param>
-    <param>
-      <key>type</key>
-      <value>byte</value>
-    </param>
-    <param>
-      <key>vlen</key>
-      <value>1</value>
-    </param>
-    <param>
-      <key>unbuffered</key>
-      <value>True</value>
-    </param>
-    <param>
-      <key>append</key>
-      <value>False</value>
-    </param>
-    <param>
-      <key>alias</key>
-      <value></value>
-    </param>
-    <param>
-      <key>affinity</key>
-      <value></value>
-    </param>
-    <param>
-      <key>_coordinate</key>
-      <value>(848, 155)</value>
-    </param>
-    <param>
-      <key>_rotation</key>
-      <value>0</value>
-    </param>
-  </block>
   <block>
     <key>blocks_multiply_xx</key>
     <param>
@@ -640,61 +455,6 @@
       <value>0</value>
     </param>
   </block>
-  <block>
-    <key>foo_packet_pad2</key>
-    <param>
-      <key>id</key>
-      <value>foo_packet_pad2_0</value>
-    </param>
-    <param>
-      <key>_enabled</key>
-      <value>True</value>
-    </param>
-    <param>
-      <key>debug</key>
-      <value>False</value>
-    </param>
-    <param>
-      <key>delay</key>
-      <value>False</value>
-    </param>
-    <param>
-      <key>delay_sec</key>
-      <value>0.001</value>
-    </param>
-    <param>
-      <key>pad_front</key>
-      <value>10000</value>
-    </param>
-    <param>
-      <key>pad_tail</key>
-      <value>10000</value>
-    </param>
-    <param>
-      <key>alias</key>
-      <value></value>
-    </param>
-    <param>
-      <key>affinity</key>
-      <value></value>
-    </param>
-    <param>
-      <key>minoutbuf</key>
-      <value>48000</value>
-    </param>
-    <param>
-      <key>maxoutbuf</key>
-      <value>0</value>
-    </param>
-    <param>
-      <key>_coordinate</key>
-      <value>(320, 395)</value>
-    </param>
-    <param>
-      <key>_rotation</key>
-      <value>0</value>
-    </param>
-  </block>
   <block>
     <key>analog_sig_source_x</key>
     <param>
@@ -958,12 +718,359 @@
       <value>0</value>
     </param>
   </block>
-  <connection>
-    <source_block_id>foo_wireshark_connector_0</source_block_id>
-    <sink_block_id>blocks_file_sink_0</sink_block_id>
-    <source_key>0</source_key>
-    <sink_key>0</sink_key>
-  </connection>
+  <block>
+    <key>foo_wireshark_connector</key>
+    <param>
+      <key>id</key>
+      <value>foo_wireshark_connector_0</value>
+    </param>
+    <param>
+      <key>_enabled</key>
+      <value>False</value>
+    </param>
+    <param>
+      <key>tech</key>
+      <value>127</value>
+    </param>
+    <param>
+      <key>debug</key>
+      <value>False</value>
+    </param>
+    <param>
+      <key>alias</key>
+      <value></value>
+    </param>
+    <param>
+      <key>affinity</key>
+      <value></value>
+    </param>
+    <param>
+      <key>minoutbuf</key>
+      <value>0</value>
+    </param>
+    <param>
+      <key>maxoutbuf</key>
+      <value>0</value>
+    </param>
+    <param>
+      <key>_coordinate</key>
+      <value>(696, 155)</value>
+    </param>
+    <param>
+      <key>_rotation</key>
+      <value>0</value>
+    </param>
+  </block>
+  <block>
+    <key>blocks_file_sink</key>
+    <param>
+      <key>id</key>
+      <value>blocks_file_sink_0</value>
+    </param>
+    <param>
+      <key>_enabled</key>
+      <value>False</value>
+    </param>
+    <param>
+      <key>file</key>
+      <value>/tmp/ofdm.bin</value>
+    </param>
+    <param>
+      <key>type</key>
+      <value>byte</value>
+    </param>
+    <param>
+      <key>vlen</key>
+      <value>1</value>
+    </param>
+    <param>
+      <key>unbuffered</key>
+      <value>True</value>
+    </param>
+    <param>
+      <key>append</key>
+      <value>False</value>
+    </param>
+    <param>
+      <key>alias</key>
+      <value></value>
+    </param>
+    <param>
+      <key>affinity</key>
+      <value></value>
+    </param>
+    <param>
+      <key>_coordinate</key>
+      <value>(888, 155)</value>
+    </param>
+    <param>
+      <key>_rotation</key>
+      <value>0</value>
+    </param>
+  </block>
+  <block>
+    <key>ieee802_11_ofdm_mac</key>
+    <param>
+      <key>id</key>
+      <value>ieee802_11_ofdm_mac_0</value>
+    </param>
+    <param>
+      <key>_enabled</key>
+      <value>True</value>
+    </param>
+    <param>
+      <key>src_mac</key>
+      <value>[0x23, 0x23, 0x23, 0x23, 0x23, 0x23]</value>
+    </param>
+    <param>
+      <key>dst_mac</key>
+      <value>[0x42, 0x42, 0x42, 0x42, 0x42, 0x42]</value>
+    </param>
+    <param>
+      <key>bss_mac</key>
+      <value>[0xff, 0xff, 0xff, 0xff, 0xff, 0xff]</value>
+    </param>
+    <param>
+      <key>alias</key>
+      <value></value>
+    </param>
+    <param>
+      <key>affinity</key>
+      <value></value>
+    </param>
+    <param>
+      <key>minoutbuf</key>
+      <value>0</value>
+    </param>
+    <param>
+      <key>maxoutbuf</key>
+      <value>0</value>
+    </param>
+    <param>
+      <key>_coordinate</key>
+      <value>(416, 139)</value>
+    </param>
+    <param>
+      <key>_rotation</key>
+      <value>0</value>
+    </param>
+  </block>
+  <block>
+    <key>foo_packet_pad2</key>
+    <param>
+      <key>id</key>
+      <value>foo_packet_pad2_0</value>
+    </param>
+    <param>
+      <key>_enabled</key>
+      <value>True</value>
+    </param>
+    <param>
+      <key>debug</key>
+      <value>False</value>
+    </param>
+    <param>
+      <key>delay</key>
+      <value>False</value>
+    </param>
+    <param>
+      <key>delay_sec</key>
+      <value>0.001</value>
+    </param>
+    <param>
+      <key>pad_front</key>
+      <value>10000</value>
+    </param>
+    <param>
+      <key>pad_tail</key>
+      <value>10000</value>
+    </param>
+    <param>
+      <key>alias</key>
+      <value></value>
+    </param>
+    <param>
+      <key>affinity</key>
+      <value></value>
+    </param>
+    <param>
+      <key>minoutbuf</key>
+      <value>out_buf_size</value>
+    </param>
+    <param>
+      <key>maxoutbuf</key>
+      <value>0</value>
+    </param>
+    <param>
+      <key>_coordinate</key>
+      <value>(320, 395)</value>
+    </param>
+    <param>
+      <key>_rotation</key>
+      <value>0</value>
+    </param>
+  </block>
+  <block>
+    <key>variable_slider</key>
+    <param>
+      <key>id</key>
+      <value>freq_offset</value>
+    </param>
+    <param>
+      <key>_enabled</key>
+      <value>True</value>
+    </param>
+    <param>
+      <key>label</key>
+      <value></value>
+    </param>
+    <param>
+      <key>value</key>
+      <value>0</value>
+    </param>
+    <param>
+      <key>min</key>
+      <value>-10000</value>
+    </param>
+    <param>
+      <key>max</key>
+      <value>10000</value>
+    </param>
+    <param>
+      <key>num_steps</key>
+      <value>1000</value>
+    </param>
+    <param>
+      <key>style</key>
+      <value>wx.SL_HORIZONTAL</value>
+    </param>
+    <param>
+      <key>converver</key>
+      <value>float_converter</value>
+    </param>
+    <param>
+      <key>grid_pos</key>
+      <value></value>
+    </param>
+    <param>
+      <key>notebook</key>
+      <value></value>
+    </param>
+    <param>
+      <key>alias</key>
+      <value></value>
+    </param>
+    <param>
+      <key>_coordinate</key>
+      <value>(947, 7)</value>
+    </param>
+    <param>
+      <key>_rotation</key>
+      <value>0</value>
+    </param>
+  </block>
+  <block>
+    <key>variable_slider</key>
+    <param>
+      <key>id</key>
+      <value>pdu_length</value>
+    </param>
+    <param>
+      <key>_enabled</key>
+      <value>True</value>
+    </param>
+    <param>
+      <key>label</key>
+      <value></value>
+    </param>
+    <param>
+      <key>value</key>
+      <value>500</value>
+    </param>
+    <param>
+      <key>min</key>
+      <value>0</value>
+    </param>
+    <param>
+      <key>max</key>
+      <value>1500</value>
+    </param>
+    <param>
+      <key>num_steps</key>
+      <value>1000</value>
+    </param>
+    <param>
+      <key>style</key>
+      <value>wx.SL_HORIZONTAL</value>
+    </param>
+    <param>
+      <key>converver</key>
+      <value>int_converter</value>
+    </param>
+    <param>
+      <key>grid_pos</key>
+      <value></value>
+    </param>
+    <param>
+      <key>notebook</key>
+      <value></value>
+    </param>
+    <param>
+      <key>alias</key>
+      <value></value>
+    </param>
+    <param>
+      <key>_coordinate</key>
+      <value>(1120, 227)</value>
+    </param>
+    <param>
+      <key>_rotation</key>
+      <value>0</value>
+    </param>
+  </block>
+  <block>
+    <key>blocks_message_strobe</key>
+    <param>
+      <key>id</key>
+      <value>blocks_message_strobe_0</value>
+    </param>
+    <param>
+      <key>_enabled</key>
+      <value>True</value>
+    </param>
+    <param>
+      <key>msg</key>
+      <value>pmt.intern("".join("x" for i in range(pdu_length)))</value>
+    </param>
+    <param>
+      <key>period</key>
+      <value>300</value>
+    </param>
+    <param>
+      <key>alias</key>
+      <value></value>
+    </param>
+    <param>
+      <key>affinity</key>
+      <value></value>
+    </param>
+    <param>
+      <key>minoutbuf</key>
+      <value>0</value>
+    </param>
+    <param>
+      <key>maxoutbuf</key>
+      <value>0</value>
+    </param>
+    <param>
+      <key>_coordinate</key>
+      <value>(48, 131)</value>
+    </param>
+    <param>
+      <key>_rotation</key>
+      <value>0</value>
+    </param>
+  </block>
   <connection>
     <source_block_id>analog_sig_source_x_0</source_block_id>
     <sink_block_id>blocks_multiply_xx_0</sink_block_id>
@@ -988,30 +1095,12 @@
     <source_key>0</source_key>
     <sink_key>0</sink_key>
   </connection>
-  <connection>
-    <source_block_id>ieee802_11_ofdm_mac_0</source_block_id>
-    <sink_block_id>foo_wireshark_connector_0</sink_block_id>
-    <source_key>phy out</source_key>
-    <sink_key>in</sink_key>
-  </connection>
-  <connection>
-    <source_block_id>ieee802_11_ofdm_mac_0</source_block_id>
-    <sink_block_id>wifi_phy_hier_0</sink_block_id>
-    <source_key>phy out</source_key>
-    <sink_key>mac_in</sink_key>
-  </connection>
   <connection>
     <source_block_id>blocks_add_xx_0</source_block_id>
     <sink_block_id>wifi_phy_hier_0</sink_block_id>
     <source_key>0</source_key>
     <sink_key>0</sink_key>
   </connection>
-  <connection>
-    <source_block_id>wifi_phy_hier_0</source_block_id>
-    <sink_block_id>ieee802_11_ofdm_mac_0</sink_block_id>
-    <source_key>mac_out</source_key>
-    <sink_key>phy in</sink_key>
-  </connection>
   <connection>
     <source_block_id>wifi_phy_hier_0</source_block_id>
     <sink_block_id>ieee802_11_ofdm_parse_mac_0</sink_block_id>
@@ -1036,4 +1125,28 @@
     <source_key>0</source_key>
     <sink_key>0</sink_key>
   </connection>
+  <connection>
+    <source_block_id>wifi_phy_hier_0</source_block_id>
+    <sink_block_id>ieee802_11_ofdm_mac_0</sink_block_id>
+    <source_key>mac_out</source_key>
+    <sink_key>phy in</sink_key>
+  </connection>
+  <connection>
+    <source_block_id>ieee802_11_ofdm_mac_0</source_block_id>
+    <sink_block_id>wifi_phy_hier_0</sink_block_id>
+    <source_key>phy out</source_key>
+    <sink_key>mac_in</sink_key>
+  </connection>
+  <connection>
+    <source_block_id>ieee802_11_ofdm_mac_0</source_block_id>
+    <sink_block_id>foo_wireshark_connector_0</sink_block_id>
+    <source_key>phy out</source_key>
+    <sink_key>in</sink_key>
+  </connection>
+  <connection>
+    <source_block_id>foo_wireshark_connector_0</source_block_id>
+    <sink_block_id>blocks_file_sink_0</sink_block_id>
+    <source_key>0</source_key>
+    <sink_key>0</sink_key>
+  </connection>
 </flow_graph>