Well I’ve done all the drilling, the mounting and the gluing. Things seem to be working pretty well. The magnet is sufficiently balanced that there is no shimmy at all that I can detect. I think the only thing left optionally would be to add a rheostat/potentiometer to the circuit to make a variable speed dial. I think I may just do that if I can find the parts needed locally. In a day or two I’ll be able to test it with a real stir bar and find out if it works to my satisfaction.