OK, I have the dimensions of my new enclosure roughly figured out and have it just about where I want it. The design calls for a 4" port that's 17 inches long. I've never used a flared port before, so I'm trying to figure out how deal with it. In my situation, would the whole port, including the flares be 17" long? Or would I need a 17" long "pipe" and add the flares?