I just want to jump in real quick on this subject of blocking out sunlight.
This was something I learned from old auto guy a while back. He trold me that almost all UV rays from the sun is blocked by regular autoglass (or any type of glass), that's why you don't get a sunburn on your left arm when your window is rolled up. UV ray is the stuff that cracks the dash material, or any plastic material in modern autos... not the heat.
He told me that the heat and lack of moisture in the cab is what we really need to worry about. The heat have an effect of sucking up all the moisture, which causes a low humidity in the cab which dries up the oil that's in leather or some of our softer dash material. So it's the humidity that we have to fight in preventing dash or cab material from cracking. He told me keeping a open bottle of drinking water does this real nice... and also cracking the window to vent out hot air. And cleaning things with a non-oil base cleaner, like water and mild hand soap is probably the best cleaning solution to use.
Now, I don't know how true all this is... but I didn't see the harm in going with his suggestion

But on top of that... I'm having a friend who does sewing/embroidery working on a special cab cover for me so that I can cover the outside of the upper cab space *only*... and it should fit nicely under the back seat. I'll post a picture once he's done with the prototype.
~Titan