Douglas,


With full size planes, the float/amphibious models always get a larger diameter prop.
The Cessna Skylane and the like gets a 82-84" prop, while the try-gear gets an 78-80"...

The added thrust is needed when operating from water.
It is your own experience that emphasizes this.


Water spray, or small "ground" contacts will not bother a GFN prop.

I think you should modify the float mounting to allow the use of an 11" prop.