[Serenity]

I agree on raising the deck (for a flush deck).On my 20 cutty that I just sold, I had an insulated fish box made flush to the floor that drained straight down using treaded plugs. It was located in the center between two fuel tanks. Its easy to clean fishbox and boat and no water is in hull area as everything is sealed. Might also consider painting the tank and also fiberglassing any exposed wood (if used) under deck and deck itself. Good luck on your project.