charlie b around? (air cleaner / downdraft table / outfeed table)

Charlie, I'm planning to make an air cleaner and I saw your combination air cleaner/sanding downdraft table/outfeed table in a Google search. Great idea. I like the idea of the getting 3 functions from the same floor space.
A couple of questions: I was wondering if placement in the room really makes a significant difference in an air cleaner's performance. I've seen others suggest hanging the air cleaner from the ceiling, by a wall, so it sets up an "circular" airflow pattern around the room, to circulate more of the room's air. A combination setup, being used as an outfeed table, too, most likely is limited to being somewhere in the middle of the room, since that's where the saw is going to be. How does yours work in the middle of the room? Have you experimented with different room placements and noticed a difference?
The truck air cleaners you mention on your web page - have you tried these yet? Do you know how they're rated for efficiency or what size particles they're able to filter out? And since they're no longer usable on the truck, how much life do you think they'd have left in them?
Thanks a lot. I already have a blower and plywood. The biggest question for me left is what filters to use to filter the small stuff (~ 1 micron) without spending a fortune.
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