Hello Ian, I can't tell you anything about an STI on floats as I have never seen or heard of one on floats. I think it would make a great float plane as it has a larger and higher lift wing than the standard Kitfox SS. But, the standard wing works very well as it is. Knowing personally how well the standard wing works, I would expect the STI wing to work just a bit better. It will however be slower than the standard wing in cruise. With all that said, I don't think you could go wrong with either model Kitfox for a float plane. Just do everything you can to keep it reasonably lightweight, as that is pretty much the holy grail that applies to float planes. Especially if on amphibs. Paul