2. Smaller scoops mounted to the column and positioned near the wheel
and close to the chuck. I've experimented with this and it works quite
well for fine grinding and the lighter particles from heavy grinding,
but the heavier grit slips by. I suspect the air velocity is not high
enough to deflect the heavy bits that are not headed toward the
suction inlet. I don't think there's much to be done about the
velocity, so the next thing I might try is to make the nozzle larger
and perhaps aimed more downward towards the chuck to cover a wider
spray of swarf.

This the current arrangement.
http://www.suscom-maine.net/~nsimmons/news/Dust01.jpg
http://www.suscom-maine.net/~nsimmons/news/Dust02.jpg

You look to have a pretty good arrangement and good plan to improve. Just
wondering, is your vacuum partly clogged? Pretty easy to do. I cleaned up my
grinder vacuum and it went from worse than a shop vac to "suck the ball off
the trailer hitch" vac. i found hair, lint, and milling swarf in mine.

'Course you could go wet, and have another whole set of issues.

Karl