My Hangar 9 Cub flies perfect with an OS 52 FS. I have flown in it with a 48 FS and an OS 70FS. I fly with a 13-5 prop. I loved the 48, but the 52 just performed the best; flying around at half throttle is a great way to spend a morning flying. If I were to try float flying, I suppose the 70 would be ok, but the 52 could still get her off the water. I just can't see overpowering a Cub. You are really cutting into the mount and cowl with the bigger motors. Big motors on Cubs seem to make good YouTube moments.