Well, this isn't going to work for everyone, but I just discovered a powerful boost for my DC. I have a Grizzly G1029. It is 2 HP with a 1450 (I believe) CFM rating. Oddly enough, it comes with a 5" port. If my math is correct, you can't get 1450 CFM through a 5" port if you wanted to.

You may have seen my recent thread about 6" PVC pipe fittings and how I needed to make my main pipe larger. In 5" size, my only option was metal piping. So, I contacted Grizzly because I found an odd thing on their website re the G1029... you can get a 6" port on it. The tech wasn't sure if it would fit, but I can tell ya, it fits perfectly! For $18 or so plus shipping, I got a replacement part with a 6" port. So, if my math is correct (and from what I have heard) I ought to be able to have two 4" blast gates open at the same time and still get close to their maximum CFM... or at least a heck of a lot closer than than before.

Anyway, my old 5" port was on a round face frame that was a little over 14" in diameter with 12 screw holes and the replacement with the 6" port was the exact same size.

Yeah, I 'm sure there are those who will tell me that I didn't increase things by much (and I know why...), but it let me run my 6" pipe, so ttttttttthhhhhhhhhhhhwwwwwwwwppppppppppppppptttttt ttt!!!!!!!!!!!!!