My only experience with a single central float was a top-flite kittiwake, and it wa squirrely. But, I may have been doing everything else wrong, too.

There were a lot of single-float seaplanes in WWII: The Grumman Duck, EDO, Japanese Rufe, the WildCatFish, and the spotter-plane they shot off the catapults on Battleships...can't remember the name right now.

Anyway, it can be done, and really it's very little different from a seaplane like the seamaster.....flying boat single hull, wingtip floats, etc.

THere is an annoyance factor to consider if you have a low wing, getting the wing on and off between all the mounting struts for the mono-float. But that's true of low-wing planes with two floats also.

I'd suggest a v-hull float. I think a lot of the reason the Kittiwake was so squirrelly was bacause it has a flat-bottom float, and it was catching the edge. A v-bottom will skate a bit once it's up on the step.