Love the look of your proto float. I would mount the servo on top and have linkage outside float avoiding any thru hull problems. I made a set of the flight test floats and used minwax plus acrylic to water proof with good results. I’d like to make a set similar to yours since they look more elegant and I suspect will be lighter. I’m working on gear attachment using carbon fiber (arrow shafts from Walmart.
How To Design Planes