Keep in mind if you ever want to use Atmos or DTS:X, being up high totally ruins that experience.
It is made clear in the ATMOS documentation that bipoles etc are not recommended for ATMOS use . A direct radiating speaker is required and the placement requirementis entirely different . Its clear from the OP's original post he is running a conventional 7.1 system. A lot depends on how wide your room is, if you have sufficient distance to either side of the seating position a lower location may work just as well,in a narrower room going up helps make the speaker less localized.
