Experimented with a few top-down burns this weekend. With standard burning, I normally get the stove top to 500F, close the bypass damper, and watch the cat light off. However, with top-down burning, I have to get the stove top up closer to 700F before the cat will light off. I am not sure if this is simply because the top of the stove gets hot much earlier than anything else in a top down burn (after all, the fire is started very close to the top), or if it's because of the heat sink provided by 40 lb. of cold wood sitting below the started fire. I suspect it's a mix of both. Once the fire is going, it's beautifully controllable. In fact, I was running with the stove at nearly half throttle all day today, and it was holding about 500 - 550F on its own. In a normal burn, where I'm reloading on top of a coal bed (rake forward), and burning bottom-up, I have to set the air control much lower to maintain 500 - 550F. Overall time from cold start to cruing is maybe only 30 minutes. I'm sure I could be quicker than I am using standard practice, but my normal evening routine starting cold takes more than an hour to go from cold stove to cruising.