One other thing to keep in mind with a chuck roast and all the meats you smoke for that matter is to let them rest properly before carving/shredding. I know it's hard sometimes but well worth the wait. This lets all the juices redistribute and keeps your meat very juicy. I myself am guilty of being impatient at this stage but when I can controll myself I'm always well rewareded. I'd also recommend chuck roasts to beginers as they are very forgiving to fluxing temps and over cooking (kind of like a pork butt), they're pretty hard to mess up.