RE: add foam to prevent sinking?
On my float planes, I run a wire cable from one of the engine mount bolts to the landing gear bolts, just in case. Doing that saved my OS 70 4 stroke from going to Davey Jones locker a month ago. The water level in the lake suddenly rose 30 feet and knocked my plane out of the sky. [&o] The engine, mount and firewall were hanging by that wire when I retrieved the plane.