I have a lot of overpowered airplanes, but in the past couple of years, I have been changing out all my seaplanes to 4-strokes. My old Sig Fazer on floats started with a Tower .46 and I flew it that way for 4 years before replacing it with a Saito .72. I liked the plane much better. The torque of the 4-stroke seemed to get it off the water very well and it pulled well in the air.

I don't know if it's the fornt vs. rear carb, but a little splash seems to kill the 2-strokes a lot easier than the 4-strokes. Personally, I'd go with a 4-stroke on the Cub seaplane. Save the 2-strokes for land planes.