I have the 2HP (so it says 2HP) Harbor Freight dust collector. I have the Wynn filter sitting on it with the bag under it.It has a 5" hose coming out of it going to a Thein "Top Hat" separator.Out of the separator it goes down to a 4" connection that has about 18" of flex hose and then to a 10' section of 4" pvc .At the end of the pvc it goes to 4"pvc again and about 6' of 4" flex hose then to a V shaped box that I made .(I have mixed thoughts on this box but have other things to try there....a big gulp and a smaller V shaped 6" thick "box"....My ? is would it make that much difference to change the 4" to 5" pvc???? Thanks in advance!