Originally posted by locoworks
guessing you got an ARTF bronco? no matter. you don't have to bother with mixes on the ZAP. there is a screen you can get up that allows you to assign any channel to any control stick/knob/switch. on my bronco i had 3 channels assigned to the appropriate joystick axis, 2 rudders and the nose wheel. use subtrim to match the centre positions and atv to match the rudders. by having a low atv on the nose wheel it made ground handling great. full rudder with minor nose wheel movement. i actually had it set in heli mode so i could use pitch and throttle curves to balance the engines. i'm not sure if the normal trim switch affects all the channels though. have a play 
No no no... (I think
)
If I remember correctly, if you set the Aux 2 to function off the rudder stick, it will do that just fine. However, 100% stick deflection would be max ATV's on Aux 2. However, the Rudder could be at max ATV's if the stick is at 100%, but it could also be at say 43% because low rates may be on, expo might be in use, or another mixer could be affecting that channel.
I do not believe there is any way to tell Aux2 to use the dual rates, expos, trim settings, or mixing influences from external mixers. Verify that you can do this, or assume it will track with the stick position, and not the Rudders desired position based on the effects of dual rates, mixers, expo, etc.
Also, I don't think the trim lever would affect the Aux 2 neutral setting, and only move the rudders trim position. However, depending on where they position the trim mixing, it might trickle down to Aux 2. Just don't know for sure.
Make sure you verify all this before going this route. I think you will find that I am right. But, I could be wrong, and there may be a way to have it track the rudders output and not the stick output. Please let me know if anyone verifies this one way or the other for sure. I'd like to keep my facts straight.