Just to update this scenario, while it's not good to just leave a tablet laying in a hot car. I have not had any problems with mine as of now 4/24/2016. I did do a couple of other things to help with cooling.
1# i drilled 2 rectangles vertically about 1 inch wide each, but not to get into the Velcro that holds the tablet.
2# i drilled 2 half inch holds in the duct work that goes to the center 2 vents. (This allows some of the air to fill the area behind the wood that the tablet is mounted on.)