Sonos Arc with Front and Rear Surrounds! How to connect! Ultimate Sonos surround system!

Ugh.  With all those duplicate channels coming from all different directions, the soundstage and directional surround effects would be a hot mess.  Rule #1 to all speaker setups - More speakers doesn't automatically mean better sound.  Rule #2 - Unless each speaker is its own discrete channel (or channels in the case of a soundbar), more speakers means worse sound.

Not sure if it would be #3 or not, but you’re also sacrificing the ability to play atmos  or lossless audio since you’ve downgraded to optical audio.   I expect both of these setups (Arc HT and Amp HT) to sound better separately then together.

But I got nice experience. I really like it!

Many people don't know how to do setup on this video 

I only gave them answer how to do.
Sonos making systems very well. Anyway in Sonos App you have many settings to correct delaying sound or speech, and you could fix it, if you will get this problem. But I didn't get delay problem.

Yes. You are right I lose atmos.  But my prector only has 5.1 sound trough HDMI ARC. And 5.1 with 7 speakers: 3 front (with front Arc) and 4 rear is fantastic.

If you’re happy with it, then great.  For the money spent though, I would have gotten an HD Fury Arcana or similar product that can extract HDMI-ARC audio from normal HDMI, so that I can retain atmos audio.  And since it appears that you have access behind the walls  and ceiling since you installed in wall speakers and a projector (ceiling mounted?) you probably could have setup a fully wired system to get much better performance.   Connect that setup to a Sonos Port for streaming audio if needed.

Also, mounting the Arc below TV without any gap is not advised, since you’re blocking the upfiring speakers. I suppose it doesn’t matter in your case, since you aren’t going to use them.

Anyway, took a look at the first bit of your video.  Honestly, I imagine you’re getting a unique sound with the setup, and maybe that’s something.  There isn’t really a ton you can do with that space, as you mentioned. I think an Arc w/sub and maybe some surround if you can find space for it in the back would have been a better choice.

HD Fury Arcana could split audio into 2 hdmi? For example one will go to arc, second will go to front AMP

First of all, stop pimping your video, it’s against the TOS.  Second of all, I have a friend who setup their surround sound with the rear surrounds on top of their TV stand.  They think it sounds awesome, I think it sounds horrible.  Either way, it’s not the way the sound was designed to be heard, which is how most people want to view/hear an artwork.

Moderator Note: Removed video for legibility of thread