I'm with BBQJoe... Smoke for a couple of hours and then crank the heat. The higher heat speeds the cook and helps to crisp the skin. Take some cheese clothe and soak in a bit of white vinegar and drape this over the bird to keep it from turning too dark. The vinegar helps keep the clothe from sticking to the bird. 12# turk in about 5 hours. It is done when you can "shake hands" with the leg. Take the leg and wiggle or twist it just a bit. If it is loose in the joint and the juices run clear, it is done.