I can to get to 350* in a decent amount of time, but it seems like that next 50+ degrees come sooo slowly. I have tried various settings on the primary air lever; rearranging the wood so I get more flames; damping down etc. What am I missing? Like right now I have a good fire going and lots of secondary combustion also, but the thermometer seems stuck on 340-350* I'd think it should take less time to go from 350 to 400* than, say, from 200-350*.