So, got the LAST piece of the Owens Corning XPS up today. By Sunday I hope to try glueing up the first piece of celling paneling. Need to figure out how to mark it for the puck lights, and get the wiring in place for that beforehand.
I can already tell the benefit of the insulation as I've kept the interior as warm as possible with a 1500W electric heater for 3 weeks as I've been glueing and epoxying. For the first time, it's shutting down periodically at the medium setting now. it used to run 24/7. The roof is the highest heat loss and the best place to put good insulation, and it shows.