This is a beginners forum... therefore, DON'T use an oversize engine.

Maybe once you learn to fly the oversize engine would be OK... but NOT for a beginner EVER.

The appropriate replacement 4-stroke for a 2-stroke .46 is appx .54 ci. .72 is WAY out. The appropriate replacement 4-stroke for a 2-stroke .20 is a .25.

Beginners with overpowered planes learn bad habits. If you have never flown a .40 size Cub with a .35 on it (they do well) or a Sig Kadet Sr with a .40 in the nose... (or some similar combination that can't hang on the prop EVER) you probably haven't learned some of the power management which can save your airplane in case of an engine problem.