FWIW, Cubs love 4 stroke engines. I have the Hangar 9 80" Cub with a Saito .72. I can take off in about 20 feet if I want to, but can also putt around at 1/2 throttle. That draggy airframe needs a lot of prop to pull it, which is exactly what a 4 stroke gives you. Plus it sounds cool and doesn't use as much fuel. If you use a 2 stroke you will have to use less pitch to get a big enough prop on it. It won't fly badly at all, but power application is not as smooth IMO.