Sadly, I have yet to do this. The Atmos setup I would like to pursue seems to not be supported by my AVR... a driving factor in my plans to upgrade.
On my right side with the low-slope, I will be mounting on the wall. My left side will require something special.
I am also considering using front and rear height positions now because of my room (so considering 5.x.6), and adding Top Middle in the wall mount locations described.
Something to keep in mind as you look at your room and how to set up speakers is that we all have some limiting factors to deal with. There are tradeoffs with our own decisions and spaces. Using the guidelines given by Dolby but adjusting to your own space is quite often necessary. The trick is in following best practices where possible, experimenting with less favorable locations where necessary, and deciding on the value of the tradeoff.
Obviously, if SQ suffers because of the tradeoff, don't do it. But there are ways to solve for many of these issues... it just becomes a matter of priority, then, whether you pursue those solutions.
So quibbling over a few degrees, in my opinion, is pretty much meaningless. Getting close, as close as you can within reason, is fine. Using a High-Wall mount as opposed to an in-ceiling Speaker, if that is all you can do, and it works in your space...
is fine.