IMO the Do will never be very precise,not in the wing design or the fuse for that matter,its not worth that much trouble to make it fly straight,do the best you can with some trim,mixing and just use it for its intended purpose:very slow flying,good 3-D'er in low wind,only fair to poor for IMAC/Pattern at best. Its worst at trying to add snaps to any straight line maneuver. I still like my Do, I just dont try to make it what it isnt.