I see a similar question has been asked before, but the answer wasn’t sufficient.  I’d love to purchase a pair of ERA300 speakers to use as surrounds, but their placement is suboptimal (to put it lightly) relative to what Sonos suggests as proper placement for these speakers as surrounds.  I also have the option of installing 8” Sonos Architectural in-ceiling speakers instead.  Not sure their placement would be optimal either.  Full info:

• I already have a Sonos ARC (about 6 months old)
• Distance from TV (and ARC) to main listening position: 13 ft
• Room continues beyond the listening position another 20+ feet into an open dining room and kitchen
• Room width 17 ft
• Ceiling height 9 ft
• Ceiling speaker location: 9 ft wide, about 2.5 to 3 ft behind the head at primary listening position.  This is pretty far off from the Sonos recommendation for speaker placement, which is 4-10 feet behind the head and the listening position should be about midway between the soundbar and the rear surrounds.
• Era300 location: There are “stem walls” or a “false proscenium” (neither is an accurate description) that is meant to provide a visual separation between the living room and the dining room.  These stick out about 22” from the side walls.  The Era300 speakers would be mounted on these.  Due to furniture that really can’t be moved, the ERA300’s would be mounted at 7 feet high, 14 feet apart from each other, and the front of the speakers, after mounting, would be about 3 feet behind the head at the primary listening position. As above, this is pretty far off the Sonos recommendation of mounting at ear height (when seated) and directly to the side of the main listening position.
• Cost: Due to installation wiring and Sonos equipment I already own, the cost of both options is nearly the same, with the ERA300 being about $200 to $300 more than the Sonos 8” Ceiling Architectural speakers after installation and wiring costs.

The ERA300 would seem to be the better option, but not if they are going to sound wonky mounted as I described.  We already have some ill-placed ceiling speakers left by the previous owners that are directly overhead the main listening position that I am currently using as surrounds.  With some effects it is really weird and the ceiling speakers make their location known, but most of the time these do the job amazingly well despite their odd location.  Therefore, I’m thinking that installing the new Sonos 8” ceiling speakers another 2.5 to 3 feet behind us will work fairly well.  (One would think I could mount them even further back, but that isn’t an option.)

Thoughts on which way I should go here are solicited.  Will the ERA300’s work properly for surround mounted in that suboptimal position, or should I go with the Sonos 8” ceiling speakers?

Thanks!