You would think by now I would not make this mistake, but I did. If you want a sub 300 degree cook, don't start too much charcoal. If you have a large amount of lump fired up, even tiny vent openings won't keep the temp down. I started a fire in about three spots and left the lid open to go prep ribs. By the time I got back to put them on, there was a raging fire going. No problem I thought, the KK isn't heat soaked because the lid was open; I'll just crack the vents, put on the cool heat deflector and the cold ribs, shut the cool lid, and get the temp at 250. The temp stabilized about 305 with just tiny slivers of vent openings. I could not get it lower. I really thought that airflow control could keep a lower temp with even a lot of charcoal going, but that is not the case. The ribs were OK, but the point is just start a little lump for a lower temp cook, shut the lid, narrow down the vents and don't let it get away. It will come up slower this way, but not get too hot.