OK, I modified the Timberline to secondary air. Tonight, it's finally getting into the 20's, so I added 5 med. splits for an evenings worth of heat. Pine, standing dead, split 6 months ago, in the sun,uncovered. After 3 hours, I shut down the primary air screws to approx. 3/16" gap- or a tad smaller. The flue temp. on the Condar probe has stayed at 800-850f. for the last 45 min. I'm showing very little visible smoke out of the pipe. Does it sound like my secondary air is working? I have visible flame lines on the tubes, but my doors are solid cast, so I can't tell when they're working. I can hear a "whooshing" sound, sometimes a low rumble from the front of the stove in this scenario, and see a small "V" cut in the wood when I stack it high- at the port areas, but I'm not certain. Can anyone with a glass door comment on this, as to any noise heard, or whatever. I'm thinking I may need to decrease my tube diam., for the secondaries, to increase the the air velocity, thus giving me a more robust air influx. I'm really guessing here, as I can't visually document this thing. Yet. I appreciate any and all comments. Sincerely, The jack*ss at sorta high altitude, who can't leave well enough alone.