On all my SPADs, the ailerons should move about the same up and down. This is xrays first SPAD, and I think he's building a Debonair. In that design, there is a single servo driving both ailerons. The Servo is on top of the wing, so it pulls the elevator up, and pushes down. My guess for the cause of the differential is that the push rods are flexing. Try using a number 4 rod (4-40) if you're not already. Also, work the aileron hinges to their extremes a few times to loosen them up a little. Make sure you have completely removed the strip of coro where you cut your hinge.

Brad