Lower Rear Quarter Patch Repair

Aftermarket parts fit like crap. Original parts fit like crap. Your chosen method of replacement is unorthodox.
At some point you just need to start tacking and beating things into submission. Be prepared to un-weld some tacks. I do admire your enthusiasm. This is a huge project. You will be using copious amounts of filler to make it look right. Nothing wrong with that if you use proper techniques.

Lap welds are generally easier for a novice. I would go above or below the bodyline,never directly at the bodyline itself. I would have tried to use the whole panel and put in at the roof seam. Easier in the end. Sometimes the shortcut takes a lot more time and effort and it not as quality a repair.

Thank you both, I very much appreciate the feedback. I'll also elaborate further. My first cut is a rough cut so I could start the fitment. My plan is to make a final cut 2" above the top body and use a flange tool so I can lap weld the greater portion of the "skin". It looks funny now, but when ready to attach will look much like a quarter panel skin would. For the first several inches where it meets the door, I plan on butt welding. I read that this method helps considerably with accommodating the transition around the door jamb, and, I have less material between 2 body lines there and want to split the difference. Let me know if my thought process needs some adjustment.

I really didn't decide on this approach as a shortcut by any means, but that it was in my amateur opinion the process that would yield me, with my limited skills, the best results. I used the rockers as a mini test, the drivers side was all butt welds, the passenger was a lap weld. I found out quickly that lap welds were much easier for me to control.

Really good to know about tacking it in place as work on the fitment. I was thinking I needed to have it perfect before welding. Once I have the final cut I'll do this as needed.

Here is a pic to help with my description. Again, advice is greatly appreciated. Rear Quarter.jpg