Everyone is assuming you want differental in the ailerons. There is also the assumption that you are using dual aileron servos. If not, then you are limited to mechanical differental from either the servo arms/wheel, or location of the horns. Aileron horns do no necessarily line up with the hinge line to achieve differental. It also maters if the wing is on top or bottom of the fuselage when done mechanically.

You may find that most airplanes needs a slight amount of differental in the elevator travel as well to achieve equal sized loops with equal stick movement.