SOME computer radios won't have the trim include function as the 8103, 9303, 10X have.

My JR652 is a 6ch 5model radio. You can mix the elevators together, but only the master servo (elevator) will respond to trim inputs. The slave servo (gear) will not trim up and down with the trim tabs.

Thats why I moved up to the 8103. Run a mix on PMix5 or PMix6 and you automatically have trim included on both servos.

I'll use my 8103 for dual elevators and 2 rudder servos. Run them on PMix5 for the elevators and PMix6 for the rudder servos. Works great. Simple. Let the computer do the work. Thats what it's for. I don't use Matchboxes unless I have too--like on the Pitts with 4 aileron servos.