On mine, I mounted the servo and installed the aileron.. Then I centered the servo arm... Then I installed on end of the control rod on the servo arm, made sure the rod was parallel to the servo using a right angle of the bottom of the servo... Then I placed the control horn on the aileron against the rod.. Made sure the control horn leading edge was even with the front of the aileron and drilled
the holes... By placing the control horn against the rod it prevents any binding at that point.. Works for me, I am sure there are other ways of doing it though..