Most of the problem I've heard with a separator with 6" holes is that it tends to suck all of the chips out of the separator & on into the DC. By the way I have the same DC from back when it had 5" a entry into the impeller.
I built a sheet metal enclosure to set on top of the bag rim & got to used diesel truck filters free from a trucking company & set them end to end inside the enclosure I can now feel the air flow at the throat plate of my contractor saw. The enclosure allows the air to flow from the outside of the filters to the inside & on up through the center & out the top. I have a heavy mill plastic garbage bag on the bottom with peel & stick foam seal tape where the bag clamps to the bag rim. I hope to have some pictures on my web site in the future.