Guys,

  Do like the factory did, and drill elongated slots in the bumper bracket's
mounting holes, then snug up tight all the washered-bolts while holding the
bumper to it's rearmost position in the slots.  (use the original bumper
bolts and washers or get grade 10.8 or 12.9 hardware)
  When you have an impact, it'll absorb some energy as the bracket slides
inward along the slots, before it bottoms out and starts deforming the
frame/ brackets/ bumper/ etc.  A mild impact will absorb most of the force
and allow you to reset it outwards again later, while with a stronger
impact, it may help to limit the severity of the damage a bit.

my 2 cents,

Mike B.

> would be for show mostly The guy that's welding all this for me was
> certified to weld on nuclear subs, so I have confidence in him.  He
> also said that  any rear impact of great velocity would shear the
> bolts holding the bumper and shove the channel up in to the rest of
> the cavity before crumpling the rear of the van.
>
> DM&FS