Thanks for making it sound like I really thought this out and it was a very scientific approach but the truth is that's the amount of plywood I had.
I also wanted it to be tall enough so that I could add some shelves for more space if I needed it. I would use some sort of rack like in an oven if I made a shelf. Don't know if I will ever need it though.
Yes, the material is Dynamat, I think. It was left over from the Factory Five Cobra I built. I guess that's what FF uses.