There are often questions about fuel tank designs; so, here is what I did with my 1989 Z-33 Donzi. The original tank is 200 gallons and that has been changed to 140 gallons. The original was the traditional tank with foam around it in a cavity. My design had a flow through cavity from front to back with the tank sitting on 3/4 inch thick by 6 inch wide by 14 inch long neoprene rubber strips. The tank was made with flanges on each corner and held in place by stainless steel bolts with nuts on both sides for stability. The tank is primed and painted and it stays dry. Corrosion is not an issue. This tank was installed in 2003 and as you can see it has maintained it's integrity.