Hello Mikey,
The same things apply to hanging speakers as they do to locating any speakers: proximity to room surfaces (the ceiling and nearby walls) will affect the sound. The closer the speakers are, the greater the effect, which may or may not be objectionable.
The dispersion pattern will change somewhat, and might even be flattering, what with all that spatial stuff happening. I know that with my M80s, when I lie on the floor to do back exercises, I get terrific imaging and soundstaging that's very different than when I sit in front of them. I actually prefer the sound of them when I'm on the floor, but that's sort of impractical.
Could you put them up on a couple of stepladders (be careful, those suckers are heavy) at about the proposed height to see how they sound?
The VP150 has no significant effect on your TV--projection, direct-view, whatever. The mass of the VP150 enclosure and the TV cabinet are sufficient to damp any spurious vibration.
Regards,
