The dang forum keeps hanging up on me tonight. Anyhoo some folks put a probe thermo into the meat for the whole cook and some like me just cook the stuff for a while and check it with a Thermapen til it gets to 160*. Whatever works for you is the way to do it.
I don't bother with a thermometer when doing fatties. Just watch the bacon (if you use it) and when it starts to turn crisp, start checking. I use an instant read digital thermometer and just poke it in the middle. If not to 165 degrees or so, give it another 15 minutes. Hope this helps.