There’s no way on Sonos devices to separate the height channel, so (short answer) no. 

Sonos only allows one set of surrounds. The Era 300 already contain the height speakers for Dolby Atmos sound. Once you remove the Amp as surrounds and pair the 300s, the Amp and ceiling speakers have to be configured as another “room” and therefore will not produce any Dolby Atmos content from the Arc. If you were to group them with the Arc, there will be a slight delay that may not be pleasant.

Hi nik9669a

Cheers for the quick reply.

I am aware that height channels are not available.

And I am aware that what I am asking about might be a sub-optimal setup.

But I was hoping someone might know if it is possible to run the amp as rear (or ideally side) channels simultaneously with Era rears.

If anyone knows I would appreciate any definitive answer.

Thanks

16. S I only included the comment regarding height channels in my initial post to rule out discussion of this as I am aware it is a requested feature that is not available.

Thanks Pools-3015

That seems pretty definitive.

It is a shame the amp can't be used for height channels.

Is that on a roadmap somewhere or just a pipe dream?

I think it’s a dream for now because I feel Sonos is still betting on the speakers with up firing speakers being enough for most home theater setups. 
This is only my thoughts, but Sonos is not trying to compete withHT systems that use separate speakers for everything. They are in vested in an elegant wireless (sometimes wired) setup that produces audio that many would be satisfied with. 
Sonos is not real high end audiophile equipment, but for me it’s the best in its class for whole home audio. It’s also addictive.. I can’t stop buying them!

I can’t afford it right now, but I am eying the Ultra to replace my Arc and move the Arc to my basement.