Mike,
How do your like your in-walls for rears? I had less trouble tweaking for acoustics (in my particular application) when I was running 4 in-ceilings in far past.
Now with a 6.1 speaker setup, -someday to be 7.1 when himself gets in the attic. (7th speaker gathering dust for a year) I have more trouble getting my acoustics in the room tamed. Yours may be on the vertical vs the my old ceiling install setup (for my orginal 4) but just seemed here...something about the attic install helped simplify my tweaking in the past, even though I had the detriment of not at ear level ideals. If my orginial 4 in-ceiling were in the proper location for a 7.1 setup, I would have liked giving the in-ceilings a go for my backs.