Today I went through 8 Dewalt batteries grinding the welds on both sides. Then I went through with a light on the backside to find pinholes- marked, tacked shut, grinded, and repeated until the panels were fully sealed again.
I also did the work on the radius before finishing the weld and doing the grinding. I was able to get it pretty close but not perfect- I was never expecting perfect and am honestly really happy with the adjustments I was able to make. The fender now mates up with the OEM quarter on the passenger side decently- a skim coat of filler and you won't even notice
Tomorrow the plan is to scuff the backside of the seam and prep everything for epoxy primer. I'm sure I have some minor surface rust since it's been a few says, so I'll also pick up some Ospho and use it in the hard to reach areas inside the wheel well area before priming. Once the primer is down, I plan on adding a layer of 3M seam sealer just to ensure it's all sealed up on the backside. Then we build the wheel wells