Figure your approximate time for one bird. You can spatchcock those and save some time. I think they come out better with a more even level of doneness. If that is a word. lol. I always do this with chickens now. Also, Poultry can be cooked at a higher temp. without any problems. You could easily do 300 or a little more and get that skin pretty crispy. I have found in the last few months that if you dry the skin really really well before you smoke it will turn out better. If you brine, which I do. Make sure to rinse them down well before drying and smoking. If you need some help in spatchcocking techniques there is a tutorial down at the bottom right of this page. Or here is the link.
What kind of wood are you using? Hickory, cherry, mesquite are very strong flavors. You may want to try something lighter on the smoke like Alder, Oak, Maple, or some fruitwood like Apple or Peach etc... I like maple for chicken. Also if the smoke is heavy, white, or brown you need to adjust something. You are looking for thin blue smoke. Also make sure your top vent is all the way open if it has one. Just some ideas.