Put it in last week, when I took the galvanized out of the chimney connection and replaced it with black pipe. Three "radiused" "T"'s and two sections of six inch pipe. I chose the radiused because they just look like they'll flow better and stay cleaner. I used the "fishmouth" (galvanized, but at the damper the temperatures should stay well below a problem, and it's not in direct contact with gasses or flame). I put a seven inch Field Controls, type RC damper on a six inch radiused "T". It took about 30 minutes with aviation snips to make the thing. Used the "T"'s at the "elbows" and will take the plugs out for cleaning... just seemed better than tearing the pipe all apart to clean it. Draft? Yeah, we got draft all right. Borrowed manometer from my cousin yesterday and last night, drilled a hole in the top of the pipe between the boiler and that BDD, and checked it. The BDD is "set" at the minimum, .02 and the actual draft is .025 at high fire and the combustion fan blowing. I believe that is the way this should be set. Should anyone have a different method please let me know. Curiosity got the better of me. I jammed the BDD closed, and without it, the draft goes higher than an inch. All I can tell you as that's as high as the manometer would go. Results? No more puffbacks and explosions... burn time on a load of wood went from 3-5 hours to 5-7 hours, depending on demand. Cleaner fire, no strain on it all the time... working stack temperatures are higher, idling stack temperatures are cooler. Boiler recovers more quickly than without it. Chimney remains clean, more or less... one little "carbuncle" way up high, at or above the roofline. When it stops snowing and warms up a bit, I will go look up there and see if I can knock it off of there and find out why it's there. Thinking maybe a crack in the chimney, but it is a 8x8 masonry, that had a 6.5 x 6.5 i.d. square stainless liner put in it from the top down. Fascinating temperature differences between the loading door and the chimney pipe... can be 525 at the door, and chimney pipe generally maxes out at 450/475 degrees and quickly begins to level off toward 425 for the duration of the burn. Builds a nice thick bed of coal now over the grates, makes loading wood a bit challenging... I level them up with my poker and lay the new wood in on top... take about ten seconds to see roaring flames in there when you turn the blower back on.