I encountered the same problem with my nexstar. its easy if you have a computer radio and adjustable end points (had mine dialled up to 140%), if you have a standard radio the fix is to install the control rod to the outermost hole of the servo arm 4th hole from the center if youre using futaba 6point star and adjust the amount of throw by turning the plastic that thread to the control rod that protrudes from the wing similar to what RCKEN's illustration.