I have a Kufo UFO-101 dust collector. It is rated at 2HP and 1224 CFM. The inlet is 5". I plan to either purchase a cyclone (probably Oneida's dust deputy) or make a trash can separator and covert it to two stage. I'm considering venting directly outside with no filter. My largest question/concern is the size of pipe. I've done lots of research and it appears 4" pipe just isn't that adequate. My shop is 30x40, but I'll probably only use about half of that for my woodshop portion, so let's call it 30x20. My plan is either to use 6" PVC or 5" metal HVAC pipe. I've seen on various forums where people run 6" PVC with a 5" inlet on the DC. But Oneida says this isn't a good idea. I bought the DC I have now on Craigslist with my table saw - it was basically "thrown in", so I don't have that much money invested. The point is I might upgrade in the future if I need a better unit as I add tools. Sorry for the long windedness - I guess my question is - is there anything wrong with running 6" PVC pipe if I have a DC with a 5" inlet? Or would I be better off sticking to the 5" metal? Thanks for any comments.