I bought my system nine years ago when I first built my 4 x 8. I made a video showing how I piped it up and built my plenum.
Still have the same plenum. I’ve surfaced the overlying spoil board down to nothing a dozen times and just drop another sheet of ULW MDF on top and keep going. I just barely moved to a new shop and had to redo the piping because I had glued it and it couldn’t move easily. I ended up using black silicone flex tape on some of the joints in case I have to change it up. Works great.