Hmm i thought but welding was welding with a small gap,i would cut out the rust and butt weld a plate in the hole,it would be flat with the weld ground down.
When i say a plate on top with a seam weld it wouldn't be flat because there would be a plate on top of the good metal.
butt welds arent the best with thin material ,joggle the edge if you want it perfectly flat
It's a footwork not a body panel ffs, cut out the rusty bits treat and seam weld a slightly bigger patch over it lather everything with some decent wallop and jobs done. I can guarantee the rest of the disco will disintegrate before you need to redo the patches.
Cheers
Whats the name of the brushable seam sealer?