I bought an 18" WSM, order a replacement top thermometer, and dual probe thermometer. I'm planning on cooking a top sirloin oven roast, can't recall the weight, but at about 225F, rough how long per pound? I'm just wondering if I need to start this Friday night, or really early Saturday morning. I haven't even figured out a rub yet, that's next on my list of things to look up. Cheers!