Foil or no Foil
In Chris's book he has a 4hr recipie that includes a foil stage, they are excellent. I have never foiled for 100% of the cook.
I usually do w/o foil, just dry rub using a rib rack to hold them on edge. 250-270 for 4.5hrs results in the meat having to be gently pulled from the bones, not really any effort at all, but it is not falling off the bone. I use a deflector and drip pan always. Try another 30min on your cook time.