I too do my own sandblasting, using a TIP 100 lbs pressure unit and a large commercial compressor, 3/4" air hose, and pressure set to 85-95 psi, and keep the spot moving, esp on sheet metal. I've never warped my parts, but I have seen cars 'commercially' blasted by people not accustomed to 'autos', that did warp every panel on the car (it takes more pressure and more concentrated blasting' than I choose to do! And even on totally stripped down body hulls and frame components, the sand STILL GETS everywhere.. and takes time to clean out of the nooks and crannies! I also have a TIP bead blasting cabinet for smaller parts, where I use either glass bead, or walnut shell particles, and I have used the Metal Rescue type of chemicals? which work well on small clean items.
The process and 'Safest Rust Remover' suggested by Charley seems a viable altenative to stripping rust of even larger items, but I suspect it's like the Metal Rescue chemicals we've all used for rust stripping smaller parts. With an assembled car, as he's proposed, I'd be concerned about it getting into nooks, crevices, etc.. even if it's 'safe'...? I might try that sometime though, as the photo results sure looked good *S*