I need advice on estimated length of cooking time and estimated smoker temperatures throughout the cook for a 12lb chuck roast on an electric smoker (the butcher claims it's a chuck roast, and the cut is likely from the chuck area, but unsure further of what it is - it's well marbleized and flexible/maliable, but a thick piece of meat). I can't find anything online with advice on how long the cook should be and how I should change the temperatures throughout. Thank you!