Era 300 inverted placement

I forgot to mention, these will be used as surrounds when watching movies. We have an arc and sub gen 3 as well. 

Have you looked at Sonos’ recommendations for speaker placement?

Home theater placement

Connect two rear Era 300s to a compatible Sonos soundbar for immersive for surround sound. 

• Both speakers' height should be around ear level and behind your seated position.
• Leave at least 8" (20.32cm) clearance around the sides of each speaker.

Yes, but it doesn’t specify in the detail I’m looking for. The recommendation quoted sounds like it’s more for stand mounted speakers. For inverted mount, it should be within 2 feet of the ceiling. Having the speakers at ear level means they’d be within a foot of the listeners’ ears. That’s too close based on the reviews and placement videos I’ve watched. 

Ideally you want them equal distance from the listening position as well as leaving the clearance Sonos specifies so your lateral position seems ok. Your ears will be somewhat lower than 2feet from the ceiling when you’re seated. I’d say ideal is at a level just below the pictures. (But that’s just about the Sonos recommendation so you may still want more detail.)

Edited to add:

you’ve added more detail to your original reply. You’re still limited by the window as to how wide you can place the speakers. Which seats do you use when watching tv?

Why put them so high and invert-mount them?

I don’t want the speakers to be too close to the listeners’ ears. I watched reviews on YouTube and they said the era 300 speakers can be overpowering or distracting if less than 3-4 ft (1-1.33 meters) away.  
 

We typically sit on either the far left or far right of the couch. 
 

It was this video. Most of the video focuses on optimal surround placement, which may include placing the speaker behind the listener  in my case, it can’t go behind due to the couch against the wall. So ultimately I’m just trying to find the best compromise  

Here’s what I chose. Also, the instructions were written before inverted mounting was fully supported. Sonos, do the instructions need to be updated at all?

Is there a setting in the app to enable inverted mounting, or does the speaker automatically detect that it’s inverted?

I like the sound but haven’t heard the alternative setups. Either way, I’m happy, and that’s all that matters. 
 

Glad you are satisfied with the Era mounting. I don’t know it you are using Advanced or Basic tuning to get the best balance of sound for your room. However, regardless of the method you use the object in the middle appears to be some type of forced air unit. I recommend turning if off during tuning.