Here is a pic. The duct is 3 x 10 IIRC. I found an online calculator that calculated the equivalent size to a 7" dia pipe. I figured heck I'm a woodworker so I ought to be able to build my own duct work! I need to paint the mounting brackets, they were an afterthought.
You could do something like this. Their is a Clear Vue cyclone in there. 5 horse. Walls are insulated. Two vents. One on top next to the light is bout 11 inches square. It makes a U-turn and goes to the motor and down over it to the MDF bracket that it's mounted to. Venting heat from motor. Vent on door comes up from near the floor. Both are lined with blue insulating board for sound deadening. Without the closset or volt as I call it, it's a jet plane. Very loud!! In the volt, I hear it humm. What I hear most is the suction from which ever port is open. All told about $2300 I can post some pics of the inside if you like.