b) drill and tap two sets of three holes at 120 degrees at the bottom and
the top of the portion of the casting in which the quill slides. Made a
half-dozen brass setscrews with a bit of weed trimmer line inserted
crossways, so they don't vibrate loose. Tighten them up and all the slop
in
the quill is gone. (Thanks for this idea, Gunner; works great.)

Hmmm. So the set screws tighten against the quill? Or does the quill slide
against the screws which now limit it's lateral travel ?

Thanks for the info !