At night, I load up the insert as much as possible- I try to pack it tight, fitting about (8) 5-7 inch splits in. Then I run it wide open, full damper, full draft, for about 20 mins to char the wood and get it started. Then, I shut it down completely- fully damped, draft closed. I find that it burns real low for about an hour, then it takes off on its own. About 2-3 hours in, the temps are soaring and the load only lasts about 5-6 hours to coals and 300 degree temp. Any suggestions about this mid-burn spike? The doors have about 1- 1/2 square inches of gap spread out that I can't close, i.e. not fittting completely airtight. Is that the problem? Thanks for your input.