Some of the bazillions of catalogs that fill the mailbox have about 2′ by 4′ downdraft tables that are hooked to the dust collector with a 4″ flexible line.  I would put a downdraft table on the shop wall and use a big fan to move LOTS of air, but there’s no wall to use that wouldn’t cause a mess outside.

Can a 4″ dust port evacuate a downdraft table effectively?  If so, I’d make one, but I’m skeptical.  Any experience out there?