You will have a much stronger and linear aileron response if you do not have your pushrod 90 degrees to the servo at neutral. Instead, the pushrod should angle in towards the servo slightly. Draw a line along the wing right against the body of the servo, towards the aileron. Then move the aileron control horn about 1/4" outside. This gives you a set-up that is strong throughout the servo travel. I'll try to find a picture...