My folks have there plasma above the gas logs mantle, and it works fine. A lot has to do with how far back your sitting. Also, if you can angle the TV down a bit, it will be fine.
_________________________
M80s VP180 4xM22ow 4xM3ic EP600 2xEP350
AnthemAVM60 Outlaw7700 EmoA500 Epson5040UB SonyUBPX800