Are you going to use the basket splitter for 2 zone heating or the full basket? The full basket will shorten the cooking time. Cooking temp can be anywhere from 225F up to 350F, depending on how much time you have for the cook. Obviously, the higher the temp, the shorter the cooking time. Most of us cook to the internal temperature (IT) of the meat, not strictly by time. For a pork butt, you want to shoot for an IT of 190F - 195F, pull the butt off the grill, wrap in foil, then a towel, stash in a cooler and let rest for at least 30 minute to allow the IT to get to 200F - 205F, for pulling/shredding. This technique will also hold the meat for up to a couple of hours, so the best advice is to start early and allow plenty of time for the cook, so as to not have hungry family/guests waiting for the butt to finish. You didn't say whether this butt is bone-in or out. That will have a big impact on cooking time. Bone-in takes longer. Also, this is a small butt, so it should cook faster that a full butt/shoulder. My best guess - at 225F - 250F, plan for about 4-6 hours, at 300F - 325F, plan on 2-4 hours.