I'll second OS 32SX engines for your project. They are a bit pricy but the engines are very impressive. They are very close to the same power as an 40FX. I use the same props on my 32SX as on my 40FX. They are very easy to tune, are much quieter than the 40 size engines and use way less fuel. I have one on my sons LT25 and it will haul the plane off the ground in about 25 feet and then pull the plane almost straight up! Forget the Wankel engines. They are very expensive, they don't have as power as the 32SX and like other rotary engines they are very fuel thirsty. I don't see the advantage of having one.[8D]