I put a brisket on the CG about 5.5 hours ago - I've maintained a temp of about 225 - 240 but I can't seem to get above 150 degrees on the brisket. It's been about 2 hours now. I know that they usually plateau but do they plateau this low and for this long? Its a small brisket - Just the flat @ about 4 lbs. Any help?