Thanks. The meats internal temp is rising steadily. It rose right through 150 with no sign of stall, so I did not foil it. I read several posts from people who tent at 175, so I might do it then.
My only other problem is that I opened the grill to check the water level in the drip pan about 20 minutes ago, and though the temp of the grill came back up, it has steadied out at 210. I have opened the vents more, but it still isn't rising.