Setting up aileron differential. This is what I do on the 12X. P-mix AUX 4 to Flap. Pos 0 set to +20 and +20. No offset. What this will do is set up so the knob will move both ailerons up or both ailerons down (while the ailerons are fully in a right and left roll). Now I got this tip from a friend, and tried it so it works. AFTER you set up your vertical up and down line trim (CG, Incidence, Throttle to elevator mix, Throttle to rudder mix, engine thrust line, etc...). This is so at idle the plane comes STRAIGHT vertical downline hands off. Then go up then push straight vertical down and full roll straight down (idle) and if the plane wobbles its out of trim. You can move the knob one way then the other way at this time to get perfectly axial rolls down. The nice thing is you can go back to the original position easily because on the 12X the knob will "beep" when it gets back to the center spot (you don't have to take your eyes off the plane). You can count the "clicks" as you put in the "differential" as the plane is rolling. Watch the nose and tail when rolling to adjust.

Why I use this is because during normal differential inputs, it limits the down on one side or vice versa, which changes your roll rate requiring a dual rate adjustment to get the original roll rate. Plus you can't trim it "real time" while flying. You can also use this technique to check up line rolls as well (again, first making sure the plane is perfectly trimmed on the up line). You can measure final throws with a throw meter and then set the differential so you can move ailerons back to neutral or, do what I do- just leave it in all the time.

That's it.