For the thickness of the floor where the deck plate is, I'll measure it tonight. My guess at the time was < 1/2".

As for the access port over the gas tank in the 2011's, it's an aluminum square the same thickness as the aluminum floor covers. It's roughly 1" thick (plate welded to square tubing), and there is bracing where this deck cover sits so that it is flush with the floor. It just pressure fits from the carpet glued to the top and sides of the roughly 6" X 6" cover.