you might be better off finding a place makes bed liners in aluminum for pick up trucks, dune buggys etc. A custom shop could probably make one for you and mount it up. I don't think it will would up costing less but probably quicker and maybe better.
Neal, ke6dcj of the 360TE AMG wagon fame had one made for the hills when he lived on the W coast, maybe he needs to see this thread?

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'95 E320 Wagon my favorite road car. '99 E300D wolf in sheeps body, '87 300D Sportline suspension, '79 300TD w/ 617.952 engine at 367,750 and counting!