HeeHee, Retransit gets the "snappy Comeback" award.

But seriously,
Normal rules of thumb dictate that the prop clear a line between the tops of the float(S) by 2", but with ONE float, you won't be spraying water at the prop. So if the prop clears the top of the float by 1" you should be OK.

The 75% rule does not apply for a single float. It should be the full length of the fuselage.

The 2-4 degree guideline DOES apply. And wingtip floats seem to dig in less if they are lower, not higher. If the float does its thing before the plane gets way out of shape, you're less likely to do a waterloop followed by a boat ride.