Mounting bookshelfs flush with ceiling - can you?

Instead of the standard true ceiling speakers for the surround channels in a 5.1 system, has anyone ever tried just mounting a bookshelf speaker flush (totally recessed) with the ceiling via attic? One can always buy a white speaker grill to cover the area in the ceiling. I imagine that a bookshelf in the $250 range (used) will sound better than a true ceiling mount speaker in that range.

Ideas? or am I way off on this concept?