RE: GP Ultimate Bipe and engine size?
Tommy, that motor would yank that plane around real well. I love 65 Sportsters. The only concern I would have is ground clearance. You can really swing some serious lumber with a Sportster. I had a 14-6 on mine in a Bingo. Had clearance problems. Flew fantastic though. I would say prop it to around 9200 rpm max and have at it.
Mark Shuman