butt welding thin metal on a curved join

Good plan!! Otherwise, "If you can't weld well, weld more!"

 

this is why I don't do woodwork, the uglies in welding can be cut and tossed and nobody can ever tell

 

You may need a wood stove, winter is on its way. Bob

 

I also have a Miller 211. For sheetmetal, I didn t see ay diffenrece between 110 or 220 v.
If you make holes, just practice as said.
I m far from a pro, but I use 0.023 with CO2/Ar or 0.030 fluxcore when I m cheap