RE: CG Chipmunk Engine
I had a ST .75 in mine and that was way more then I needed. If you broke out the shoe horns and a couple of hammers you could fit it in there with room left over. I am sure that a Magnum, O.S., GMS, TTor any other brand of .91 would fit. I do not remember if you will run into prop clearance problems.
Dru.