I have a Delta 50-760 dust collector coming and I have a few questions. I know the main inlet is 5" diameter and I would like to make the duct as large diameter as possible, but it seems impossible to buy 5" diameter fittings, (PVC). Any suggestions? Should I somehow go up to a 6" diameter or would it be more practical to go down to 4" since I don't plan on making any runs longer than 12 feet from the collector. I also plan on using some type of pre separator either store bought or Thien.