Thanks for the compliments, guys.
Tom:
I don't mold the clay around the tubes. My wife makes me a tootsie roll of clay and bakes it. I cut it, then drill the blanks out and glue in the tubes. Then, I turn them just smaller than the bushings. I plug the tubes and cast them. Then, I just turn the blanks down to the bushings. In between, of course, I print the doggie pic on a label and stick it to the clay. You end up with a very thin layer of alumilite over the clay.
For my next one, I'm not going to drill the clay before I cast it. I'll turn it between centers to just smaller than I want, cast it, drill it, then turn it down. It will eliminate having to plug the tubes and clean them out after casting.