Holly crap!!!!! did I read this right a 3.7 in a h9 72in. cap, are you sure you dont mean the 80 in. cap. I had a 46cc poulan chainsaw in mine then took it out for a 30cc stihl on glow engine and it was a better flier with the 30cc stihl, the one pictured in my avitar. If it is the 72in. I would seriously reconsider your choice or engines.

Darin