CG Ultimate 2-stoke advice
I have an os 91 four stroke in mine. I have a Webra speed 1.20/cline pump in the wings waiting to install when I get bored with the OS. Problem is I am not bored yet and I find the plane truly enjoyable to fly with the 91 four stroke. I think a YS 91 supercharged would be the perfect combo.
The Webra swings a 16 X 8 Prop at 10K and I am sure will provide plenty of wobble knee excitement.