Well, I was ignoring the obvious, which was you can feed the heck out of it while the cut is shallow. So I found that I can feed 3 to 10 thous at the start, and taper off, with the last 30 thous or so down at 1 thous and below for feed.

That should have been pretty obvious, eh?

Anyhow, I am up to about 1 toothspace every 10 or 12 minutes, with a little less audible strain on the machine than before.