This section of frame rail rotted out where the spring cup was sandwiched against the frame rail. I cut out the bad section and stitched a patch in, rather than just paste some good metal on top of the bad. I first ground both panels into a V at the joints so that I had a nice clean surface to fill with weld and more surface area for the weld to contact.
Clearly, I'm no pro welder, but the penetration is good and it grinds out fine.
I had to go to a flight lesson before finishing the grinding. If you look at the bottom of the patch, it hasn't been ground yet. I will also weld it 100% from the rear too and grind that flush too.