I didn't feel it needed a complete repair panel, just a new return flange replaced. After some discussions on the best way to do this - removing the edge and flange back to good metal would be the best option.
I started by cutting off the flange and 3-4mm of the face edge. Then making a repair panel/patch with flaps each end add strength when welded.
Using clamps I tack welded each end and inside to hold in position - then stitched weld along the edge. After some cleaning up with a flap disc it looks pretty good.
My plan with these joints and other areas is to try "lead loading" than filler.
3hrs