a great suggestion, but this is already what I'm doing. I had a roaring fire going on top of the kindling fire, goes great for 45 minutes, then tonight with the door open, it just flat out went out. My installer says we need to check room pressure first, but they don't do that, and they don't know anyone who does... doesn't want to talk about the flue going from 6 to 8 inches, he says it shouldn't matter.I'm wondering if maybe you need to let the larger pieces char and get going longer before closing the door and shutting down the air? You can't get the kindling burned down to warm up the flue and stone, then throw in bigger stuff and shut the door. The bigger stuff needs to get going good before shutting it down. This isn't to say the flue isn't an issue, but it might help...