I made a first pass at fitting the 20-ga. square wire bearing into the ring. It's a wee bit too big- which surprises me since I tried to cut it a bit short according to my calculations- but, more importantly, it's clear that 0.8mm is not wide enough to support the enamel on the sides. I suppose that it doesn't desperately need side support; I may need to think on this, since while placing 2 wires or strips along the top and bottom, spaced exactly the same distance from the surface and inside of the ring is tricky.... trying to shape a piece of sheet to the exceedingly funky inner dimensions of the space sounds even trickier.
If I go with supports on only the top and bottom, I think I should also put a "stop" in on the sides, so the enamel can't move side to side during setting.
Now, I could follow the Lap. Journal process and make an entire setting for the enamel, then solder that into the ring. The problem I have with that right now is that I don't have an appropriately-shaped bezel mandrel. I really want a rounded-corner square shape for the enamel, and I don't have that in a mandrel.
So I have some thinking to do...