On writing software for an 08m picaxe chip I discovered that the neutral position of the spectrum reciever is roughly 1.4ms as compared to the neutral of 1.5ms on the futaba 40mhz.

This would account for the need to offset your trims and the need to set the stick movement to 125%.

I also found that the Ian Inglis control board that I have used for many years would not accept an output from the spectrum reciever. The problem was solved by reading the output into a Picaxe08m adding 0.1ms and re-broadcastng the signal. It also worked by putting a GWS FS1 failsafe in the line.

Trev