Adam,
You will find that a 2 lb brisket (which is VERY small) could take as long as the ribs! It is extremely difficult to smoke a brisket that small, and have it turn out the way you think it will. Those little boogers have a mind of their own! Last tiny one (just under 4 lbs) I did took 11 hours! So, you could take up to 3 hours/lb. My advice is to smoke the ribs, at 235, for 5-7 hours (spares take longer than back ribs), and use that baby briskie for stew meat. When you get ready to smoke a brisket, the biggest you can fit in your smoker is the way to go. Anything under about 7 lbs is going to cook really weird!