I happened to notice my motor was extremely hot. I didn't even think about it getting hot - and it shouldn't! I am pretty sure that it's because the belt on the spindle was putting too much lateral pressure on the spindle. I moved the motor a bit closer, now with the belt rather loose. It's running cool now, and a side-effect of this is that the duty cycle required to keep the disc at 750rpm give or take has gone down from 48/255 to 39/255. So I guess that's a reflection of how much harder the motor was working to overcome the belt pulling on it. Interesting.
One other thing - I took the belt off for a while to see how hot the motor got when not driving the disc. And the disc just kept on spinning and spinning. I was really quite surprised - it must be SUPERBLY balanced, even though I have stickytape all over it covering holes and such. I decided to time how long the disc took to spin down from 750rpm to a complete standstill (without belt attached). It's an astounding 13 minutes and 25 seconds of spinning!! That's incredible.
Anyway, once again I really regret not giving it a glowing review when I first got it.