Forgot to add: I'd suggest cooking them to around 205 deg. I pulled mine at 195; they were good, but not quite as tender as I'd like and some of the fat hadn't completely rendered.
They were on the WSM for about 11.5 hours and got up to 190°. It was late, so I used a trick I've used before where I preheat the oven to 250 and reset it to hold at 145° after putting the meat in. They were perhaps a touch overcooked (falling off the bone) but were still pretty moist.