[bradford]

Whale, If I were you I wouldn't drop down to 40 gallons. I spent about 500 bucks and had a custom tank built. It's three times as thick as the factory tank so hopefully it will be the last one my V20 needs. I also did a better install job than the can of expanding foam. I glued 12 2X4's to the hull with 5200 with a wide channel between them in the bottom of the bilge. I then covered the tops of the 2X4's with 5200 and set the tank on top. I hope I never have to remove it because it probably won't want to come out! The 2X4's are pressure treated and the tank has plenty of room around it to allow water to drain away and breathe. When washing down the boat I pop the deck plates off and can rinse any saltwater or other crud off the tank. Just my 2 cents !