I'm thinking about sticking an O.S. 91 on this plane is this too much. A friend of mind had this .91 on a .40 size warbird, and the engine ran just beautful. All of your thoughts are appreciated.

Also, he had an O.S. but what about Thunder Tiger. The other thing is, the O.S. 91 weighs less than the .61, is that right?

Thanks,