I fly my FK on floats often. Mine are the GP 60 size and work great. The step is at the CG. Engine is a Saito 91. I have a small servo mounted in the left float to work the rudder. Drop the flaps, power up and your off easily. Drop them on landing and in a Wyoming wind you can drop on the water with no forward motion.

FYI, I am building a Giant Flyin' King. 135" wing span. Planning on floats. Will have to be about 72".