The 9C will only control 8 functions, since it's in PPM mode when using the trainer functions. So 2 of the channels in teh 12FG can't be used. Also, the channel order in the 12FG will have to be altered so that the 9C function as the student. Both transmitters have to have all functions on the same channels. That means that the special channel order the 12FG generates cannot be used. The 9C cannot have the channels ordered to match the 12FG, so you must change the 12FG.