RE: Extreme Flight 88
I've never done the pipe thing but have read where people got poor results with the wrong length header (and wrong prop). Just a guess but you should be getting around 7600 RPM on the 22x8 Mez. That prop spins higher numbers than my Xoar 22x8 beech (Mez has smaller blades).
That 110 Yak would be incredible. I have no way to do that kind of project right now. It's 50cc only for a while. But the EF 50cc planes are pretty big which is why I fly them.