Hi geno472,
I have a ST 75 in mine and it provides plenty of power for the way I fly. Whils't the ST performs very well it sounds like a two stroke

. If I were building the Super Chippy today I would wait until I could afford a Saito 82 or similar quality four stroke.
Based on my experience with the ST swinging a Bolly Clubman 12.5 x 6 the 91 would significantly overpower the model............but lots of people like that[sm=sunsmiley.gif]
Cheers,
Colin