Once again, doing the bare minimum...
The dome ring was rubbing up against the screws that hold it onto the Rockler bearing, enough so that when I tried to fit the ring to the bearing, the ring had a tendency to get stuck. The back three screws went through the holes in the dome ring, but the front three didn't fit so well.
I marked the holes that required a small bit of widening, using a Sharpie to locate where a little extra material should be drilled out.
I used a hand drill to grind the holes, making them just a bit larger.
A few minutes later, I had a good fit between the ring and the bearing. Not too loose, not too tight.
As happens from time to time, I couldn't help myself, and I did a loose fit of a bunch of junk on the droid. All the panels are just held on by gravity, as are most of the other parts. Don't sneeze. (I've since taken everything off the droid.)