I kept it on 15 for the entire cook and lifted the lid 45 minutes into the cook as someone suggested in another forum. With the wind and falling temps, I closed the lid again and waited for it to finish cooking. Total time was 1.75hrs.
I lifted the lid a few times fiddling around with the temp probes. I used two, the factory Char Broil one and the Maverick ET-732. I had a 20 degree difference in temps for the entire cook.
I pullled it when the Maverick hit 162.
I was very impressed with how this came out.