The one i had was made with a slimline pits muffler on the old version edge WH had and it swung the 18/6w apc prop at 9600 with no pump. I just tell you this because you might want to try a good pitts muffler get more rpms and not have to mount a pipe. Plus i like the 2 pipes sticking out the bottom of the cowl it looks a lot like full scale.