Lower Rear Quarter Patch Repair

I know your not done with your prep so just throwing this out there, You should be using something in between those patches to afford some type of corrosion protection. Whether it be epoxy prime and just clean up enough to weld and some weld-prime etc inside and out of each layer. I like vice grips or sheet metal screws over the spring clamps. Tighter fit up easier to weld and less chance of bumping something out of place when you can't see through a helmet.

Just in general, if your repairing or making patches you want to use the same gauge material as you are replacing. You do not want to use pieces of an 18-20g aftermarket qtr. patch panel to repair a 14-16g. structural inner rocker as was suggested.