So I went back and rewatched this video:
Acoustics for Immersive Audio This is where I heard it the 2nd time (once at CEDIA 2014 and then in this video) about 9.1.2 being preferred over 7.1.4. Now the examples at the ends of the video are obviously a bit more high end as they do 9.1.4 and 9.1.6 and even the first "9" is actually 11 speakers with 2 working both on the left side surround area and 2 for the right side surround (one for each row of seats).
So you would have to be able to drive 2 speakers on each side surround "channel" connection on the receiver to do that or use external amplification.
Anyway, I cobbled together an "updated" Dolby Atmos 9.1.2 diagram showing Dolby's location details in black, and then Anthony Grimani's real-world "tweaks" that he has devised for a really amazing experience.
Below is the stock Atmos 9.1.2 diagram straight from Dolby's website, but then I stripped out the lines and angles, and added Grimani's tweaks in red and a bunch of notes about those tweaks.
Now, this is a configuration for just a single row of seats. The video never touches on a setup for 2 rows of seats that doesn't include 2 more side surround speakers and at least 2 more overhead Atmos speakers, so it puts a limit on people wanting to stay at 11 channels. Anyway, here is the diagram.
One other interesting note is that he likes the side and rear surrounds about 1-2 feet (depending on ceiling height) above ear level, where Dolby likes them right at ear level.
All in all, this just means that you will want to experiment with whatever you decide you want to do. I might just hand on to a pair of QS8s for front wide speakers, and trade in the other pair and VP150 for a pair of on-wall M3s for the ceiling.
One other thing that came up recently is that Grimani has found that being able to point all speakers, even the overhead ones, towards the listing area is critical for getting people into the soundfield (see around the 46 minute mark in the video above). In my CEDIA 2015 video of the super high end Steinway Lyngdorf setup room, you can see that they angled their overhead speakers as well.
Steinway Lyngdorf CEDIA demo video Hopefully this is at least a clear as mud, and helpful in some shape or form.
