However, with that said, I found the best method is to put the jack just inboard of the pinchweld, but up against it. The structure there is almost 1/4in thick. You can find the thick part by poking a finger through one of the holes down there.
Edit: Don't bother buying the rubber pinch weld pad that is offered with that jack... It will get cut clean in half pretty damn quick. I returned both pieces for a refund.