It looks like fairly thick steel, probably similar to what the $150+ that bolt to the crossmember are made of. I don't see it breaking up from a driveshaft rattling around in it for a few seconds.

I have the Allstar (generic) version in a box, if I can just bend the long pieces they intend to go across the width of the car, so that they go as they do in the OPs picture, it would seem fairly stout.