We have one on our 41DS I believe it came from the factory that way though. The vent is mounted on the port side just in front of the cockpit combing about midway between the gunwale and the cabin top, the vent hose runs up to that point from the small exhaust fan through the port side closet and lazarette. I have not looked at it that close to know what size flex tubing is used but I can't imagine it bigger than 2" given the exhaust vent size. I question now as I write this what is incorporated in the design if anything that would prevent down flooding should the boat be rolled onto its side. I have used it after a long motor use day when the temps were already warm, oh I had to use that word......warm, won't see that again for a while.