You would use two 100s for bonded surrounds.  What is your intent for the other two 100s?  Sonos will only bond two surrounds and, most of the time, two subs.

I have the 100’s in all 4 corners of the room Left and Right in the front, the beam in the centre and the other two 100’s are in the rear also Left and Right. The Sub is in the centre forward.They all work without any problem setting them up, I just want to know if I can seperate the front two and the rear two so I can get real 5.1 Sound.

The Beam is already giving you 3.0 sound. Actually Atmos since it is a Beam 2.

The Sub is giving you 0.1

If you add the rear two of the 100s giving 2.0 to the Beam you will have 5.1 / Atmos. 

Adding the other two 100s by grouping will work for streaming but for TV they will play at a slight delay. The echo effect bugs me.

I was just thinking of that. The Beam 2 is 3.0 with a Left, Centre and Right. it is connected to the eArc on my TV, which is less than 6 monts old. I have a Left and Right Era100 on either side of the Beam, and then Left and Right Era100’s on the opposite wall. The Sub is under my bed….. this is for my “relaxing” so my wife doesn’t kill me when she is home. When she is out, I go to 7.2 downstairs and rattle the walls.

I turn my hearing aids off first btw. The Sonos have a lovely sound quality to them. All Era100’s and the Sub Gen 3 are wireless of course. There is no lapse in the sound and all the speakers work. I wonder what is coming out othe Era’s ??? rear sound on all four?

TV? The rear Eras are playing the 5.1 rear sound or what Atmos has encoded for them.

Front Grouped Eras, a stereo down mix of the Beam's 3 channels, I think the Grojping may be killing any Atmos improvements you'dnormally see from the Beam. 

 Most folks find the down mixed pair at the front really hurts imaging.

Good to know, I will check out disconnecting the eras in the front, fortunately they are on stands and not attached to the wall. Thanks for your help and suggestion.