Several years ago I designed high wing model which I called EASY 100. The model had 60” wingspan. Ready to fly weight with the floats was 6Lbs. The removable floats I designed started just past the prop. I did that on purpose to prevent the water spray coming of the floats and hitting the prop. On purpose I gave the floats extra volume by increasing width, so less then 1/3 of the floats are submerged. On that model I never had problem taking off or landing with this set up. The model plans were published in RCM magazine in July 1988.
From my experience with the float planes, I feel that there are several factors to be considered what will or will not work. Like the volume of the floats to support the total weight. The total weight put on the floats. The shape of the bottom of the float. The position of the step. How high the C/G is above the floats. The last but not least is the angle at which the floats sit in relation to the wing.
Laddie.