Late to the party as usual.
I had that unit in my old shop with 6" HD HVAC piping. 6" all over changing to 4" at the drops. I kept a 2 1/2" flex hose open at the blade port of my RAS, so it could not collapse the cheap pipe. Only one drop was 6", for my Jet 15" planer, and it was the closest to the cyclone.
The first time the filter needed changing, I left it out and exited through the wall. This system worked fine for me with the machines I had....Unisaw, Jet planer, small shaper, router table, RAS, 14" Band saw. I only opened one duct at a time, and had a minimum of flex tubing.
About running small sanders and whatever on a DC system...Never made sense to me to neck a 6" pipe down to less than 3/4" for a palm sander. I just use a $50 Quiet series Shop Vac with a bag in it, mounted under my table with appropriate overhead hose. Works fine for my sanders, biscuit joiner, and compact router. Haven't gotten around to putting a Dust Deputy on it yet.
Rick Potter
DIY journeyman,
FWW wannabe.
AKA Village Idiot.