It'll need to be a rectangular shape, to maximise space, I haven't got exact measurements yet.
Jez, i don't have a TIG unfortunetly, just mig, (and access to big migs B) )
If i make it from sheet steel, bend a return edge and overlap the seams, can i mig it together myself ?
I guess i'll need a lockable sealed filler cap, a feed and return fittings and a breather. Am i right in thinking that the feed and return should come out of the top of the tank ?