Just finished taking a rack of ribs off of the pit. It worked perfectly. After 3 hours the rack had picked up enough smoke flavor, color, and aroma. Putting it into the oven bag and going for 2 more hours really tenderized them and broke down the collagen. I've seen Youtube videos where, once wrapped, the pit temp is brought up as high as 300 degrees. I didn't do that. I held the pit temp at 246 - 250 degrees the entire time, wrapped or unwrapped. I unwrapped for the last hour and they firmed up nicely. Incidentally, I did not add extra moisture, like bbq sauce or vinegar and water to the bag, just a light coating of rub sprinkled on the meat side. I punctured the top of the bag 3 times with a dinner fork to vent some of the steam. Plenty of moisture was evident in the bag when I opened it.
I haven't seen a down side to it, after only one session of course. I was concerned that not enough steam would escape and they would turn out mushy but that was not the case. You can easily pull the meat from the bones cleanly but the meat doesn't "fall off the bone". After unwrapping the rack tightened back up to exactly where I wanted it. The rack bent easily when picked up by the ends but it didn't break apart. Also, after unwrapping, instead of going exactly for the last hour I went by temperature and made sure they finished at 205 degrees. I think it took only 45 minutes or so to get to 205 degrees once unwrapped.
I'm encouraged by the results and I will try it this way again next time, either with more ribs or a pork shoulder. I find it to be much more convenient and less time consuming than wrapping in foil, especially on a breezy day. Thanks for your response by the way. I appreciate it.