I don't know exactly what happened, but the ribs sucked. They cooked a long time, but they tasted a bit tough and a bit underdone - even though it would be impossible for them to underdone. Temps never got better 270 and hung about 240 most of the 6 hour cook. I'm thinking I stacked the grill too much. Not enough room between the half racks to properly render while cooking.
On the other side, the pork shoulder and chicken were fine. Just tainted from the bad rib run.
Agony of defeat.