Mike, can you post some pictures of the insides of the transmitter so we can see the wiring connections to the trim levers. I'm running a FrSky telemetry module in my Futaba 9C and a FrSky D8R-II Plus receiver and works great. Of course that is a plug and play installation and much different than what you are doing.

One of the very old Kraft radios I have does have a mechanical connection to the control stick pots for the trim levers, but all my newer radios like the 9C the trim is more like a spring loaded switch that advances the trim function when it is held in ether trim direction. If your radio is using an electrical trim, I think the connections would be to the transmitters encoder section.

There is a Futaba FG Gold Series thread on that other RC form site (I don't believe RCU will allow me to post a link) where you also posted this information. There is a FP-T7 in the thread that is working. You might want to take a look at that thread.