I seem to be having getting temps above 425-450. Everything I've read said the grill should be preheated to 500. I thought perhaps I was running ther gas assist to long on the coals causing some of them to become spent before I even dump them from the chimney. I also am not sure where I should position the lid thermometer, directly above the coals or over the area wher no coals are. When instruction call to cook something indirect over a particular temp where is the best place to post ion the lid thermometer?