Unable to add second Sonos Sub G3 to existing system

Thank you for this information, I will do some positioning tests.
 

This is my setup for now.

Lower right corner, sub #1, and the Arc to its right not visible, under the TV. And the second sub, behind the couch.

So I placed the two subs to direct the sound in this angle « \ ».

I am especially surprised by the increase in sound quality of the two Era 300s with the addition of the second sub. 

To the left of the telescope is the dining room, so it's a large open-air space. So the addition of the second sub there, behind the Era 300, acts a bit like a second room from the dining room point of view. It fills the whole space much more evenly than with a single sub.

By the way, I would not use Time as my test track. I prefer a thumpy rock radio station because there will be more “thumps” per minute.

Time, its only one track, just happy last night when all is working good 😉 .
 

I listen mix of dolby atmos, ultra hd, hd, stereo 

What is your favorite config, like equalization, and audio surround, audio sub, audio vertical?

It probably varies depending on what you listen to, style of music and, or, movie?

Only you know what sounds “best” (to you). I know a fellow who always sets bass and treble to max and placed his SUB at one of the “!!” spots that I mentioned above. He loves it. I’m so glad that I only pass through there every few years.