Hello bwallen,
I'd advise you not to invert the speakers. They are designed and balanced to sound their best in normal upright position. It also isn't how the blind listening tests and anechoic measnurements at Axiom are conducted--with inverted speakers. They will certainly sound different; whether or not the sound and sonic balance will be degraded, I don't know.
Also, the off-axis dispersion of the M80s is excellent, so you don't need to have the tweeters exactly in line with your ears. I also wouldn't invert them because it would put the woofers at the top, so they won't benefit from the boundary reinforcement for the bass octaves, thereby altering the carefully designed sonic balance in the room.
Regards,
Alan
