I would only try an overnight with a whole packer with 11 lbs being a minimum size. Fat cap down, cook low throught the night then foil in the am to finish (probe tender). Foiling helps with brisket as in the un-even thickness will render overdone on the thin end and under done on the thick end. If you have to hold, be sure to tent for 10-20min before resting so the meat won't continue to cook.