Depends on what kind of giant scale you are wanting to fly.

If it is scale aerobatics, you will not have enough power to fly an upline with snaps or any other maneuver with the power you are talking about.

I have a 26 lb Edge 540T with a 100 cc 6.2 ci engine and I wouldn't want anything smaller on it.

If you want a war bird or any other type of scale plane and want it to fly scale, you would be fine with one of the engines you mentioned.