I use 5" duct work for my portable collector. Two 10' hoses which are
connect to a 5" wye at the inlet for the impellar. One hose goes from
the jointer to the table saw, I move it depending on the machine. The
table saw has a 5' length of HVAC I bought at the BORG which puts the
end next to the jointer. Into these openings I use the Woodstock
(grizzly) 5" blast gates as they are tapered and slide in pretty well.

The other hose has a 5" to 4" reducer which I tapered by putting in
front of my propane heater and then slidding onto a floor sweep to make
a flare in it. This fits TIGHT to my DW735 and is used between it and
an adapter to various other tools like a OSS, or a vac hose, or a
sander hose.

Alan