Kirby most of the Bipes that fly well are overpowered. I had a GP Ultimate (40 size) and loved it. However the 46fx I used just didn't have enough to pull it around like I would have liked. I'd say that if you go with the DP 40 size I'd use a 4 - stroke such as a 72 Saito or a YS 63 (that would be sweet!) or a 50-60 class 2 stroke. Whatever the case I think you would be VERY pleased with the flight characteristics of the plane. It acts more like a Extra than a Pitts in most maneuvers and the large rudder makes knife edge flight easy and when you slow it down it doesn't get squirrly like some of the other bipes I've flown.

Josh