The q's are very forgiving and because they have 4 drivers firing in phase at the same time you are totally enveloped in the sound, I don't think a few feet up/down would bake a big difference. I would be more concerned about how high they will be. Also, your placement of the left/right and rears does not make sense. You need to have the left/right surrounds spaced out further to the left/right of the main couch. Also, the rears you have behind the left/right surrounds, not good, they need to be closer togethor and behind the listeners.
