RE: CG Super Chipmunk sheeting issue.
Sounds like something is wrong all right. You didn't accidentally use an incorrect piece of sheeting somewhere else, did you?
If it were me, I'd just go to the LHS and buy 4 sheets of whatever size is needed.
I had an OS 90 (Pre-surpass) in mine and it was great. Either of those engines will work well, but I think the Chippy really deserves a 4-stroke!
PS, you're gonna LOVE that plane!