My 27 PC aluminum tank sprug a leak and 1/5 of it is in the engine room the rest is under the aft cabin. I cut through the aft cabin and found the tank. Plan to remove the tank in pieces and replace with a custom plastic tank and try to seal it back up. Has anyone had simular issues/problems which can provide some advise?

Not if it matters but I found a great company in FL which makes tanks to order at a fair price and to exact specs. Installed the tank and it's all good. So if ever anyone else runs into the same issue, I have a solution.