I have inherited a Chipmunk. Now this A/C is used but complete. After installing the engine (2stroke) on the mount it seems to me to sit quite high, the prop shaft sits well above what I think would be the center of thrust on the fuselage. Were these engines meant to be mounted inverted? I don't know if the engine mount had been removed and put back on upside down. Now heres the rub..... the throttle cable comes out on the side of the fuselage perfect for a 4 stroke or inverted 2 stroke????

Most Chipmunks I've seen have the engine mounted inverted or sideways. If you mounted the engine upright that maybe why the crankshaft is setting high. Also the tank might be to low for the engine. If it is that might be a clue as to how the engine was mounted originally. Nice plane. Good luck.