Hi Joe,
I took my old 2hp Reliant DC and "rewired" it to take on the 6" ductwork. The unit's mounted in my garage with a 26" straight run into the impeller that's bolted to the concrete wall. I then reworked the bag ring and bought the Process Systems filter bag. I also use a plastic garbage bag on the bottom with an old cloth bag to reinforce it against tears.
Had some damage to the impeller when a full size screw driver got too close to an intake. Had to have it down to the weld shop to have 3 fins straightened and then the thing spin balanced to 3,500 rpm. (Had to get a new screw driver as well. Man, that was LOUD 😱) Runs pretty quietly now, but my wife complains that if the interior garage door is not well latched, the air pressure will blow it open and she has to put all her weight and push hard to get it closed again.
The Reliant was a house brand for the old woodworker's warehouse chain. Made in the same Taiwan factory as all the rest, but it has an 11" impeller instead of the 10" fans others used. Here's a pic or three of the set up. If you can locate you collector outside of the shop, you'll improve your shop air quality a great deal, even with 1 micron-rated bags. You do, however, have to be careful of reversal of drafts on such things as water heaters and furnaces.