So I woke up around 3am and noticed temp was slowly dropping and had reached 210. Popped out and slid the bottom vent over a touch (I had it around 2 match stick heads).
Opened the top a little more and went back to sleep.
Woke up and it settled at 250f and was ready at 8am just in time to wrap it and sit it in an Esky while I take the kids to preschool. Annoying that the temp dropped but I'll know to leave bottom vent a touch more open