Ted,

This may help.  The FmX will not port NMEA out the rear ports IF the AP controller is part of the system.  It will only go out of the laptop 9 pin connector that is part of the controller harness and thus configured in that area.

If the FmX is running stand alone in "manual guidance" mode the settings in AgRemote will then stick and be usable.  Also while the typical 9 pin uses data GND for pin #5 and the two DATA pins are 2 and 3.  Contrast to that on the FmX Port C those pins are GND = 5; and the data pins are 3 & 4.  If transmit and receive are not handshaking 3 & 4 can easily be switched around in the DTM connector eliminating possible Null modem adaptors.

While the 750 only has two ports the assumption is it has parrallel approaches but I have not messed with that yet and most likely the firmware will be more robust over time.

Arnie