At the risk of starting a firefight on the thread, I wonder if the water cup story is so terrible implausible (in general I mean, not case specific).
What Bob Hoover was doing was essentially keeping a constant and steady 1G applied by effectively doing a very precise barrel roll, effectively the opposite of the "vomit comet" ride where negative G is kept applied by a prolonged bunt, BH kept positive by prolonged and constant back stick on the way around and balanced by maintaining the same roll rate. Thats why most of us would struggle to emulate the move, we would displace the water by varying the roll rate, the rate of G applied or both.
BH's demonstration therefore, IMHO, does not discount that water will move in the glass when experiencing change of forces, it just demonstrates what a perfect touch he had/has.
Whether water in the glass can be used to keep the sky the right way up or not.....well who is volunteering to go out and test it in VMC with a hood and a safety pilot....then publish the video results on here
