RE: options for GP Cessna 182 .40.........
How much is it supposed to weigh?? If it's designed for a .40 I would say with floats a pro .46 would be just the ticket if you want to stay with a 2 stroke and scale flight.
Just my .02 cents worth. and purely speculation based on experince with .40 size airplanes and and .46 size motors. water has a lot more drag than wheels on grass.
Miloh.