I just cut the bottom (new top) out of two kegs tonight. I drilled a pilot hole then pounded a finish nail (the kind with no head) into a 2x4. I nailed a second 2x4 onto the side of the first and clamped my angle grinder to the "extension" 2x4 to get it back to center. The boards were oriented long way up. This worked great, and took less than 5 mins per keg to cut the tops out with a 1/8" cutoff wheel. The best part is that the pilot hole I drilled was perfect to braze in the screw for a cabinet pull that will serve as the handle on the cutout, which I made into a lid. I'll do the same to the second keg tomorrow.