Here is a shot of the driver's side floor pan. The chassis "main rails" are 4 inches tall, just like an original car. I say "main rails" because the structure is somewhat like an airplane with longerins and ribs. The floor is connected to the top of the rail and the belly pan is connected to the bottom of the rail to make a very strong box like structure. The stressed tunnel adds to the stiffness and the tall door sils add as well.
