I know there has been a few threads on this. I can't seem to find a definite answer. I plan to smoke a 18 pound 7 bone Prime rib at 225 degrees and then crisp up the outside in the oven. CAn anyone tell me how long it should take to smoke at 225 for 18 pounds to get the middle to medium rare? I've read 30 minutes a pound to 1 hour a pound, so i'm just confused.