The idea of having a sanding disc that could be mounted to the lathe (as others have done) seamed to get plenty of interest. I figured I would start a new thread to show where I'm at. To finish it I need to get some steel. I recently switched trucks and don't have a rack for the new truck so until I do or if I need the table it'll probably just wait. Right now I'm leaning towards not making the table tilt (other than being able to adjust it to be at exactly 90°). The table is from an old Craftsman tablesaw that a friend was going to throw out. I cut the hole for the blade out and bolted the two halves together. The table is just set on some blocks to see what height would work best.
disc 1.jpg
disc 2.jpg
Here's a few pictures of the MT#2 adapter holding the chuck with the cole jaws to flatten the bottom of a bowl (most likely would never need to do it but it would work to flatten a segmented ring). The one thing to note is that the adapter must be seated well into the tailstock or it will spin. The maker says to use a 3/8" threaded rod to do it. You can't leave it in place and use the handwheel on the tailstock to move the chuck. You either need to use the rod to pull the adapter tight and then remove it or leave it in and slide the whole tailstock assembly. I think it comes down to how accurately machined the adapter and the tailstock's MT#2 are.
disc 5.jpg
disc 6.jpg
disc 4.jpg
The last picture is the rim of a bowl after flattening it by holding the bowl by hand against the disc and another one to show what the before looked like. Over all I would say it works well.
disc 3.jpg