Currently I am working on a 25 Fordor. Under the rear seat is a metal sheet that covers the opening and the rear spring. There are tabs around the edges of the metal sheet. What is the purpose to the tabs? Did they hold a cardboard type covering in place to dampen noise?
They held a heavy fiberboard mat.
Where do you get the mat
Another picture from Adrian Whiteman's posting on the Time Warp Centerdoor. The Fordor is pretty much the same. I would use some of the bitumen board that is used in the upholstery industry.