My son had a GP42 on his and wanted more power. So I got him a saito 72 for it. He loves it. 4 strokes make them fly different. Unlimited vertical. I had a KB 61 on my 4* 60 and changed it to a Saito 91. wow Flys much wilder with the 4 stroke. 61 had lots of power but not torq like a 4 stroke.

Randy