There are some new rules coming out about 2nd row occupant crash stuff which will apply to newer models in the coming years which got me thinking about installing a sacrificial impact panel on the 2nd row driver side. Mercedes will have to upgrade that crew van option to comply moving forward. I think the law is regarding interior panels and having no exposed metal in a passenger area including the roof. Disclaimer- this is all my own home grown engineering, anything you do to your van is your own liability. That said I used trunk liner to carpet the factory panels and installed 1 1/2 crash foam laminated with a bubble foil radiant barrier on both sides in the window depression. The thinking is the 1/8" factory panel is weak enough to give under a side impact and the foam acts like a bike helmet. Better than a exposed metal panel in any case. In hind sight the 1 1/2" foam was a bit thick with the radiant barrier lamination.