Excellent on the trainer choice its a fine airplane and it will serve well on floats. In addition the forty LA will be perfectly fine on that airplane even with floats. I happen to have a much heavier airplane an old plastic ARF trainer called a Ready Two the does great on the water even with that engine.

Its not required to use bigger engines in most cases but what is important is the float selection and positioning on the airplane, in other words the struts and strut positioning orientation is the key to a successful floatplane.

I have enjoyed float planes for years and even have just finshed a fifty mile floatplane cross country flight down the Colorado river last weekend. But I do recommend flying on wheels first and becoming competant that way before going to floats.

John