I have a 1973 Ambassador 29', my question is about the holding tank under the toilet (it's a back bath), the tank is not leaking but it looks enclosed in sheet metal. The sheet metal is rusting away, the holding tank seems fine, no leaks. Should I get rid of the sheet metal enclosure? How do I fix this? Is there a purpose for the sheet metal? Can I take it out or patch it? The big problem is, since it's rusting out/away, it's putting pressure on the aluminum underbelly making it sag. Advice please!!! I have a sinking feeling this is going to turn into a nightmare!!!