My dealer said that the SL-300 isn't made to run bare over the roof. While I do like the look of a roof chase for chimneys, I'm wondering if this would be necessary. I don't have complete trust in my dealer, as we've had a few disagreements, for which they make recommendations against the the owner's manual. So the question is, does the air-cooled Sl-300 need to be enclosed all the way to the termination cap, or will 3-5 feet of exposed pipe be satisfactory?