Aluminum HoldingTank?
Assuming the problem was an aluminum holding tank, there are numerous posts in the Archives, some may be specific to the 35.5. However, check the size and location , the difficulty in removing the existing, match the location of fittings with a polyethelene tank, etc. Then possibly you can get specific answers to specific problems ---some Hunters have a poly tank, some are built into the hull liner and some models had aluminum but the metal tanks are notorious for problems.