Surface area of the liquid/air boundary should have an influence, logically.
Bottles upright will have only the cross sectional area of the bottle as a state boundary.
Bottles on their side will have a larger surface area boundary. Worse, I would think.
I squeeze the extra air out (which mashes the bottle in and limits surface area). Seems to work, but YMMV.
Sounds like one for the Mythbusters. As long as they can make it explode at the end.
