Not to piss in your coffee, but I bet any difference in the sound probably falls into the psycho-acoustic range. The Qs are so diffusive (not to mention the woofers are still pumping out "localizable" frequencies, by and large), that changing the position probablky just results in a slight tonal difference, rather than a different spacial feel.
That said, what do I know? I would think that, for the side surrounds, the more diffuse sound field would be preferable. The rear surround, though, might be different.
Have you tried spinning the rears only? You might get some neat localized sounds from the rear of the soundstage with Dolby PLIIx.
Interesting experiment.
