Welcome back to the forum AZ! With 2 hours 45 minutes in the smoker at 250, plus another 40 minutes in a convection oven at 400, your chickens were way overcooked. 40 minutes in a convection oven alone would probably be enough to roast 2 whole spatchcocked chickens, much less the additional smoking/cooking time. I think if you trusted your original temp probe and pulled them from the smoker at 165, they would have been moist. Did you rest them for 20-30 minutes before you determined that they needed more cooking? If you are talking about the skin on the chicken being tough and rubbery, you are absolutely right! Skin on smoked poultry is inedible (in my opinion, but my dog loves it!). The meat on the other hand should be moist and succulent. Hope we can help you get some chicken success! Chicken has become one of my favorite things to smoke on my #1, because I can brine and smoke, all in one day, with little advance planning or prep.