What I would like to do since the new one just drops through the hole is to make it in two halves. it could be larger and fit under the lip. the first half would be pushed forward under the lip and would be wider for a water tank. the back half would be a larger holding tank. I could then use the old holding tank spot for may A/C if I get it figured out I will post more.
That derelict boat was another dream for somebody else, don't let it be your nightmare and a waste of your life.