The two modifications that I made to the Aerobird Challenger is a Pro Tail and skiis for winter flying. The Pro-Tail is made by placing tape across the slot between the control surface and the stationary part of the tail, filling the slot with epoxy, then wrapping the tape over the top to keep the epoxy in place. Once the Epoxy is fully set, cut a new slot beginning at the old slot and going toward the front of the tail. The entire tip of the tail becomes part of the control surface. Adjust the location of the control lines through the control horns for differing amounts of response. I have mine set all the way in, and at full throttle on the stock batteries the plane is a handful to control. For details on maiking the skiis, go to my Skiis thread in the ParkFlyer section.