though i worked as a welder in my youth, i'm a long way from a pro. like the idea of going heavier gauge for the patch. of course mig comes to mind. if stick, go w/rods recommended above, reverse polarity, make say 1-2" intermittent beads, then either come back to weld, or use high quality sealant between. (rod technique & angle, not lingering in puddle for long but for adequate penetration) can also keep the heat from blowing through.... clean sand/grind prep is what it's all about too. let us know how it goes