Den said:BK prefers to highlight long burn times over high output. A 6" flue might be adequate for this, but they still have to allow for Homer jamming the thermostat open and burning 80 lbs of wood ASAP in an attempt to make it throw heat like his old smoke dragon.
Den, that is exactly my current thinking on the matter. I've considered the issue seven ways from Sunday, as some folks have noticed, and the only negative consequence I can come up with is reduced maximum burn. It seems to me that if a 6" chimney were otherwise optimal, its response and effects would be similar to an 8" chimney with a partially closed damper--good draft and minimal effect at low to moderate burn/flow rates, but the maximum flow/burn rate would be reduced. In other words, the stove would work fine and burn the same at low/moderate rates, but its maximum output would be reduced. That would be just fine with me, because I want the King over the similarly rated Princess for the longer burn times.
Thoughts? I've asked BK the same question, though I'm afraid they won't say much besides "don't do it" out of fear of liability exposure with no upside.