To me the best way to ensure it is cooked properly in the center is first to saute any veggies that you plan on using like the one I made yesterday with onions and mushrooms and second place the probe of your Maverick or whatever you have in the center while cooking. Once it get close, then check it with the Thermapen. I smoked the loin yesterday in a mini WSM at 275. The veggies help keep things moist as well as the melted cheese. Took a little less than two hours. BTW - the other meat is some grilled venison medallions.
WSM, 99 & 09 Performers, 2-OTG, SJG mini WSM, Summit 420, Q100, Akorn, and Schwenkgrill