The thing's a monster. This build was designed with efficiency in mind, but I question the lack of catalyst. It allows you to basically reburn the volatiles as a secondary fuel, instead of going up the stovepipe and condensing as solid creosote. If you stick a catalyst before the heat exchanger section you'll drastically reduce the creosote accumulation and you can get an extra 30% BTUs out of your firewood. For such an efficiency focused design I'm wondering why there's no provision for a catalyst. I think they might even be mandated in some areas now.