As usual there were a few details to attend to before welding. I drilled a bunch of 1/8 in. holes to weld through, then fiddled with the grinder, hammer and pliers to get a good fit on all tabs. I also cleaned up the tabs and the border of the hole where welding would take place, to get a good weld.
When everything was ready I painted both sides of the patch with Weld-Thru primer and worked out how to hold the patch in place by wedging tapered punches in from underneath. The welding went well, although burning through the thin original metal was a problem. I lowered the current to just over 3.
After some initial grinding I identified several places that would benefit from a second round of welding. After more grinding I filled everything with POR-15 Epoxy Filler. Since I had a little time left I went ahead and covered the small holes with two layers of fiberglass set with POR Patch.