Kind of goes with the territory unforunately Grant...I've done most of those repairs on my 55 2nd series. My first welding of patch panels ever was the corners. I had good looking patch panels. My first welding job came out excellent. After gring the weld you honestly couldn't tell a repair had been made.. I have that disease when I don't know when to quit..so I gound them a little more until I gound thru the paper thin metal. Finally cut one side off and bought another patch panel. It wasn't even close to looking like the one on the other side. That detail that is a continuation or the rocker panel varies quite a bit from supplier to supplier..size wise..and the degree of "crispness". Anyway I eventually made the new one look like the other with some creative welding. I think most of us accept the idea that we will have to do this from time to time. My rocker/step combos were real nice and came from Rico's Rods and relics. I feel your pain..Dig in and get to work unless you want to start auditioning sheet metal parts..
Good luck and have fun
Keith