So I'm smoking a brisket for the first time today and decided to place one of my weber remote probes through an onion on the cooking grate. I've got all of the bottom vents closed, but am still getting a reading of 269 degrees. The built in lid thermometer, which I typically go by, is reading around 225 or so. In reading temperature tips on the how-to, it states that it should be higher at the dome than the grate...which temp should I go by? I don't want to cook at too hot a temp and have it come out dry, but I also don't want it to take forever... I was hoping to achieve a cooking temp of 250...