You got yourself a great plan there and don,t be shy about getting help from a mentor. I,ve tested a number of new Lazy Aces for folks with everything from a K&B .61 to a G-26 gasser and they all were ladys. The .91 would probably be OK for the Tiger Moth but can,t say for sure. The only real problem would be if the engine weight caused an CG problem and that I doubt.

John