xray328, you have built a trainer aircraft, so it is in your best interests to have equal amounts of up and down movement in your ailerons. To achieve this you have to position your servo arm { if it is a straight one } parallel to the aileron, so you then have equal amounts of push and pull, with the aileron in the neutral position when the control on your radio is also in neutral position . That includes the trim levers as well. Only when you are advanced enough to fly high performance aircraft will you need to program differential control surfaces.