Late today I purchased a wireless thermometer and as is normal for Over The Top ... I installed the wireless unit between the insulation and the silver metal roof. This was at 5:30 PM late today. Tomorrow it will be much colder so I will have to wait until it gets hot again for additional test results.
My bet is, the silver roof will hit 130 deg F easy. Here again is where I tell you at this temperature your solar panels will loose 50% of their output. I will also experiment with spraying cold water on the roof to see how it brings the temperature down. I bet none of you have ever thought about cooling your RV or panels down by spraying water on the exterior, it is very effective because water absorbs heat very fast.
It's now 8 PM evening and both temps have equalized. Once fully insulated the opposite readings should happen at night. Maybe 60 under the skim outside & 75 inside. Time will tell, I plan to install more wired units.