Skeptical:
- I haven’t seen many roof racks rated for 250lbs.
- I don’t like failure mode of this sort of hang – drop you on your spine on a metal bar
Cheaper, lighter, less wind resistant:
I often hang mine from one hinge of my hatchback to one good tree/post/pole… Used to do it with a Honda Civic hatchback, now a Subaru Forester. Works well, if you can get your rear end the right distance from said tree/post/pole.