Rtparr, I've been making and selling foam core floats for nearly 5 years now and I have created a spreadsheet to calculate the displacement of a float. If you can give me some detailed dimensions, I will plug them. I need info like width at widest part, at the stern and at the nose. Height at the same 3 places. Flat bottom or vee bottom. Depth of step. And of course total length of float and length from step to nose.

Stickbuilder, look at www.geocities.com/planefunfloats . The length of float should be 75% - 80% of your fuselage length measuring from the prop to the rudder hinge line.

Seaplane