I have been flying the WM Midget Mustang for the past year with an OS 91FX. I absolutely love the way this plane flies. Simply point it where you want it to go and it goes there. I have found that cutting out more cowling than usual is necessary to increase air flow. If I had a complaint it would be weak landing gear. Mine would bend back and as I taxied my plane back to me it would ultimately tip over. I replaced the landing gear and it does fine now. As far as servos are concerned, I use Futaba standard BB's in mine and all controls are clean and crisp with no flutter. You will enjoy this plane.