My left/right side surrounds are mounted about 9ft up near the ceiling in my basement, rears are a bit lower, and everything sounds good. They are very forgiving on placement, and once setup correctly in the receiver settings, should sound fine. I suppose you could rig something up using the Axiom brackets and an extension to lower them a bit if needed..

M80s VP180 4xM22ow 4xM3ic EP600 2xEP350
AnthemAVM60 Outlaw7700 EmoA500 Epson5040UB FluanceRT85