Joann,
I think your next job will call for custom welding work. Stick to aluminum
for the tank and battery frame/s. Surely someone can weld up an aluminum
frame from angle stock that will allow your batteries to sit side-by-side in
their cases with the small propane tank mounted above them. That won't take
up too big of a footprint on the trailer frame.
About that swiss cheese frame? I'd get that fixed with metal scab patches
welded to the frame. Make sure they clean the area really well of any rust,
etc. first. A good welder can have that frame looking like it was never a
piece of swiss cheese.
Tom
WBCCI 5303