Holding tank or Fuel for Jeanneau
I was made to understand by waste tank makers that Plastic was the best material then stainless was second. And that regular steel was the worst due to corrosive chemicals in human waste. In any case, at 18 gauge it isn''t going to corrode anytime soon, and ( very importantly - despite what makers of plastic tanks say, all plastic based tanks get odor permiated and smell through the plastic, just like the best hoses do.. But there was another consideration, the cost. I contacted two of the biggest and best plastic tank makers...Ronco and the other escapes me. Both wanted around 2000 dollars. Mine was built for a third of that!
Lastly, you are right about having so much potential weight up in the bow area...if the tank were full or even half. But the point of a holding tank ( for me anyways) was to have the convenience and legality of a place to store wate ONLY while at the dock or in a harbor. I , like most anyone I know would certainly pump-out at a station in harbor before setting sail, or dump legally beyond the 3 mile limit, so the weight up front is not an issue.
It would be for a fuel tank. But your estimated weight of 900 pounds I believe was way off for a 50 to 65 gallon tank. The bottom line is in 50 foot jeanneau''s where the builders were more concerned about quick turn around chartrs in waters not requiring holding tanks, there are few practical options of legal sanitation devices that would serve a live abord like me well at harbor or anchor( without having to go to the pump-out dock every few days. Jeanneau has a optional 5 gallon holding tank you can buy but you have to give up you closet as that is where it goes with its plumbing too. That''s it! 5 measily gallons. No, I''ll take a NON smelling huge stainless tank hidden away over the factory idea. But I would like to hear from more on the stainless holding tank corrosivness.