I think I'm still a bit confused. The drawing (as shown) seems to indicate equal throw for up and down ailerons. Don't we want more up than down? Do you set the end points to enable more up than down? Sorry if this seems obvious, I just want to be sure. Also, you all use a Y-cable to make this happen?
If you have a computer radio and dual aileron servos, you can program aileron differential if you choose. If you have dual aileron servos on a 4-channel NON-computer radio, you will need to use a "Y" harness to connect them and the only way differential would be possible is by placing the control horn pivot point behind the hinge line. Dual aileron servos does give you more control authority and also some redundancy should one servo ever fail.