I just got the grinder with wire brush wheel out to clear away some of the rust to see how bad the damage is:
https://www.aulro.com/afvb/images/im...2011/09/13.jpg
If it were one or two holes I would have considered a Knead-It type product to patch along with a membrane inside the tank but as can be seen the rust was hiding quite a bit.
I am leaning towards a custom tank, either steel or aluminium, but its just a matter of finding someone to make it and certify it for me.

