Enough procrastination.   Time to weld the floor patch.   Here is my first practice piece.  It took me a while to work out the right settings and technique.  The circled one is pretty good.

So I did another practice piece.   I experimented with longer beads and shorter ones.  Longer put too much heat into the part and risked a burn-through.   Plus all the welds need to do is hold the brace in place.  The seat bolts will provide most of the strength.

Time to do this for real.   I bolted the brace to the patch.  To help keep the patch panel from warping I clamped metal bars to the edge.  I don’t know if it will help but it seems like anything to absorb heat and keep the edge straight has to help.

I just made little stitch welds.  After each weld I used compressed air to cool off the weld area.  It turned out pretty nice!  And there was no warping of the sheet metal.

Here is the top of the panel.  Good penetration by the welds!   I cleaned up the part, masked the edges, and painted the bottom side.   That has to dry before I can weld this in place.  I forgot to take a picture of that.  I also ordered some seam sealer and I might put that on before I weld it in.  That will be the next challenge.