After I got all 4 pieces fit I painted the inner panel with Rust Bullet and then I started tack welding the pieces in.
After I put a couple tacks on the third piece, I removed the Clecos so I could get to the remaining edges with the welder.
All 4 pieces tacked in.
Since my welding is not a thing of beauty, I finish welded it all up with the MIG welder and then ground all the welds before taking another picture. Now all it needs is a skim coat of filler.