I used the white 6" PVC,it wasn't a problem to hang alone, I made my own plywood hangers that I screwed to the ceiling. for blast gates I used the single CV clear plastic 6" ones then reduced to 4" at some of the machines and then to 2 1/2' to others. When I open the 4" or smaller blast gate, I always open another 4" to provide make-up air flow in the main duct to keep from getting any settling out in the main runs. I didn't glue the joints, taped most with the aluminum foil duct tape.
I only have 3hp w/ a 12" impeller, your 5 hp w/15" impeller will suck the socks off your feet with your shoes tied. Be careful not to stand too close to an open end.LOL