Well, I don't know. I've never actually set a larger engine at a lower rate to see how it goes. I think that if I were you, I'd get a 61. I know that there are people out there that will put such an engine on this plane, but from what I have seen, the airframe just can't take it. If you don't break a linkage you'll pull the horns right out of the balsa due to the extra thrust in manuvers. Its your choice but for the 150 bucks it would cost for a decent 61, I'd just buy a new engine.