I just put GP .40 size floats on mine. The one day I flew, it was OK, but, not the power I wanted, with a .46. I have just mounted a .61 on it, but haven't flown it yet. Hopefully this engine will compensate for the drag of the floats. Biggest flight characteristic I noticed was inverted flight. It climbed like it was tail heavy and it isn't. I think it is more the float incidence in relations to the wing incidence. I will keep you informed of the way it flies with the .61. Then you can decide if you want to change your engine.