Doc
I thought about this last night and I think I well completely machine that raised ring off the recoil shield and then use a thicker piece of shim stock to make the new ring from.
I'll make the ring about +.160 in diameter as the original raised ring on the recoil shield. That way I'm clear of the nipples and have more surface area to support the back of the cylinder.
Silver solder and brass melt as about the same temps I think. I plan on using what they call low temp silver solder.
Check this low cost
gas torch.
I use one for very small items, the O2 bottles get spendy and don't last a long time. A full size gas setup works but you need the smallest tip you can find, a 0000. I don't know if they make any smaller.