Ok I am going to change a few things....
I am not going to plastic off the inside of the cab (only the floor) or even mylar the walls, not even paint them with fungicide paint. Nope.
I am going to use elastomeric white roofing sealer!!

Will make it air tight, has over 90% light reflection,, will not need to caulk, mildew and mold resistant, and it is able to expand and contract from heating and cooling. Love this Idea. I bought some mylar lastnight (never used it, only white paint and the IR block) What garbage that shit is to work with (and no it was not 1mil)
I am also ditching my reflector that I made. It sits atop my old cab and would have done the same on my new cab, but I decided to make a cool tube. This will make things much easier. but more expensive being that I have to put more money into my setup. But as I have said before, "Make what you can (within your means, not rigged), buy what you can't, don't let money be an issue, it all pays for itself in the end."
