Ok If I am understanding you Make sure that from the center of the servo to where you attached the push rod are the same distance same from were the ailerons are hinged to were the push rod connects to the control horn have to be the same Finally are all of the servo arms at 90 degrees from the servo when in neutral and I think for this to be exact you need the same length pushrods
If you have the capability with you radio It probably would be easiest to run top and bottom ailerons on separate channels and adjust the servo travel limits accordingly Hope this helps