It does sound like the same specs as my Harbor Freight DC, although I'm not using any permanent piping. I'm just using a 20' x 4" flex hose, and I move it from machine to machine.
If I were doing a permanent installation, I'd probably go with as big of PVC as I could get away with...hopefully 6" for the main lines. Any smooth pipe will likely be better than flex hose. Not to be contrary to Bill, but I've read a lot of concern about static electricity in ungrounded PVC, and a lot of evidence to indicate it's not a problem. (For one, you can't ground a non-conducting material, as far as I know.) It's one of those never-ending debates, and the only right answer (in my opinion) is to do what you feel is best.