How not to !!! rear lower quarter panels

Also remember the patch panels are sometimes less gauge than the originals, and the originals have rusted over time from the INSIDE! and are thinner too!!! It is thinner metal, that means when you make the cut down below the character line it is somewhat flimsy. I like to see how it will all fit together when I use metal screws to attach it all before I begin to tack weld. Also . 023 wire (must use gas) is easier to weld with than .035 and not distort. Basically few people should try to mig weld with .035 on this outer skin, and gas shielded wire welds cleaner.
Sometimes a piece of something inside that lower patch can be useful to maintain a straight surface before tacking or screwing together.
Some people will say butt weld it! But there is a flanging tool that will help get a flat surface too. One thing is if you overlap, only have a minimal amount, and treat with a weld thru primer.
I am no expert but all this I have found helpful over the decades.