Hi Mudman, I have the Clayton, I think its a 1600. Its not the biggest one, this one has the 6 inch flue pipe. I do not have a barometric damper installed. The chimney draws like crazy but I have no way to measure. I know that when in the basement I can open the clean out and hold the door about 3 inches open and the chimney will suck it shut pretty hard. (Interior chimney.) I burned that time for about a day and a half with shaking only, temp outside was about 35- 40. I was so proud, I thought 'this isnt so hard' but then in the morning I found the same old problem -coals dead around the outside of the bed and just a small glow in the middle. I didnt know that it was possible or necessary to block the above bed air holes. I quess I could just put bolts through them, didnt know about that. I really appreciate you guys helping me with this!