Nice pictures Warren - love the turkey - pretty pink dress and a nice rack! :lol:
I used a Flexovit metal disk (only one was needed) on my keg shaped vessel a couple of weekends ago - I had a diamond tipped disk but decided not to use it unless I chewed through a shitload of metal disks. As was said in earlier posts, let the disk do the work - don't get medieval on the cover, just run the disk over it to make a deep score and then go back when it is a bit cooler to finish off the cut. I held the grinder upside down and let the top of it rest against the rim - keeping it vertical allowed a nice even cut all the way around.
I worked the lid off in less than 5 mins and there is still enough of the disk to make it useful to clean off small jobs etc (yeah, I know, tightarse!)
I have a Morse brand 7/8ths metal holesaw with built in arbor and a pilot drill bit - picked it up from local plumbing supplier for about $35 - will punch a hole in the keg this weekend in preparation for installing a weldless SS bulkhead fitting - getting closer to AG brew day now!
Cheers,
TL