I have an old 38 UTS MM that has a bad gas tank. It was pretty good everywhere except the bottom on one end where it rested on a rubber pad is all pitted and rusted through. I cut out that area and made a replacement piece to weld over it but it has to extend over to the edge where the metal is doubled and maybe rolled but when I try to weld it there I just melt the solder out of the old seam or joint. Is there any way to fix this, can I solder my piece on good enough to hold? It is about 6 inches long and the full width of the tank and I curled the ends to follow the rounded tank curve. Any ideas would help. Thanks