[Mike K]

I've seen situations where certain fussy restorers do the plug weld, grind flat then use a small spot drill to replicate the small dish that a genuine spot welder leaves on the panel. It never looks totally convincing though , because the genuine spot crater has a slight dish or cratered shape to it that is not easy to replicate

The welders at the local TAFE were 3 phase things..... like night and day the difference to the average home setup struggling with single phase .. your grandmother could do perfect large welds with those industrial machines.

When I built the new Land Rover tailgate I used a common household adhesive on the Alu panels.. it's still holding up good as new years later despite being out in the weather . I visited Ian Duddy the Land Rover body builder and he showed me the method of spot welding he uses on Alu panels ... and all he had was a medium sized small factory spot welder.