Jammy, I think the question about the Hi-Lift J-attachment is can you lift the van using the stock bumper- will the bumper take it locally (not dent) and will the bumper support the van (not bend permanently).
I used to lift my trailer with a hi-lift to release the pressure on the tires- it's a dual axle trailer and parking it on the cement slab would cause the tires to be twisted pretty hard. I'd jack it up on a "solid" part of the fender just in front of the wheels until the tires lifted ever so slightly. The seventh or 8th time the metal wall where I was jacking just collapsed and bent out about an inch.
I'd hate to be the first guy to start jacking up the stock rear and have the bumper just crush into the door because the manufacturing specs are different from the days of bumper jacks.
This is the J hook by the way:
So--- Jammy, I agree with you about the hi-lift being a good jack (I own like 6 of them). Where can you jack on the rear aluminess bumper?