Era 300 Placement - Long rectangle room. 300's pointing at each other and cannot swivel enough.

Speaking from experience with speakers in general they are not designed to face each other as they will have a cancelling effect. The surrounds are no different. Depending upon the angle TruePlay may help (or not).

I would try TruePlay and also turning TruePlay off and setting the distance to the sofa manually in the app. In both instances you need to have a movie ready with lots of surround material to test. (Dolby Atmos or at least DD 5.1).

Yours might have been the one situation where I might have recommended in-ceiling speakers for surround positioned over the sofa (assuming the angle of non-adjustment for the Era 300’s is severe). Although, you would not have Dolby Atmos effects from them as you have with the Era 300’s.

Let us know how the surrounds effect sound after you try my suggestion and if you kept TruePlay on.

Thanks.  I Had 4, 15 year old Paradigm speakers in my ceiling and opted to forgo a Sonos amp and go all wireless Sonos (which I have in my family room).    The Sonos ERA 300 mounts only swivel a small amount, and my concern is the speakers when swiveled towards the center of the room will be “smashed against the walls” and affect immersion.  It’s a tough space with the 4 reclining seats directly behind the sofa, and not being able to use stands.  

An extendable swivel mount, like an extendable swivel Sanus mount that I have for my TV, might be a good addition to the Sonos mount options.

I missed the fact that there were 4 recliners otherwise; I would suggested placing the in-ceiling speakers over them. Your space may be better suited for a traditional home theater setup; as you probably had before. Sonos sometimes is not the best option. 

Yeh, maybe I do stands behind the reclining seats (to the left and right) and tell the 10-11 year old's to be careful…  I’ve removed the old speakers from the ceiling, patched the holes, and painted the ceiling black.  So that ship has sailed.

Why not put up a couple of small shelves, with the Eras sat freestanding on them? Check the Era guide for wall spacing minimums to be sure you have the needed clearance, depending how much you want to angle them.