Speaker placement was dictated more by not wanting the TV up high on the wall, not wanting the centre sitting on the A/V unit, and the need to clear the Hi-Fi speakers.
I know that the accepted norm is to have the centre speaker below the TV, but I have no issues with it being above, it's only a couple of inches anyway.
You can't see them, but the left and right speakers are the exact same height as the fronts and wall mounted to either side of the listening position.
The 2 rear surrounds are the only speakers to not be wall mounted. They're on a shelf of a bookcase about 4 feet behing the listening position (sofa). But they are almost the exact same height as all the others.