Float length is 75% of fuse length from the thrust washer on the motor to the rearmost part of the rudder. Float distance apart from center to center is 15 to 25% of the wingspan. 15% is scale. Most people go with 20%. Float step is just behind the CG not more than 1/2", 1/4" is better.... When you install the floats, the horizontal stabilizer should be level with the top of the floats, with no incidence. The wing incidence will take care of it. These settings will have a setup that you can run across the water at full speed and will take just the tiniest bump of elevator to get you in the air for nice scale take offs. You don't need water rudders unless you plan to fly somewhere where it is really windy all the time. If you want them for scale looks leave them up.