Drew posted a description of the frame twister test you're thinking about. It looks like this:
Does the sound come from all over the car? All 4 doors? Just 1? I can make some guesses (have had a couple noises that could be characterized as plasticwrap scrunching), but only if the sound's localized

Insofar as your current experience, I don't see how that could be a possible culprit - there's not much torsional action going on just climbing a paved hill! Certainly contracting seals could be, however.
Does the sound come from all over the car? All 4 doors? Just 1? I can make some guesses (have had a couple noises that could be characterized as plasticwrap scrunching), but only if the sound's localized