After hearing QS4's as mains before my M80's arrived I wondered about the potential of using them as dual centers, one above one below the screen.
Then the thought went off on a bit of a tangent.
Lets just say a guy could afford QS4's or QS8's for each position...
I don't know what I'm thinking. I do want to hear your pro's con's do's and don'ts...
and..go...

Being that the design of the Q's is to envelope/wrap you in the sound, not sure they would work well for center purposes and dialog in movies.

One?
Gotta give it a try.

As far as a "would it work" perspective, I don't think I'd use QS8s, as those are 6 ohm speakers. You'd end up presenting a 3 ohm load to your receiver/amp, which is a tad low, unless you have a pro amp.

That said, I'm sure someone around here is nutso enough to run a pair of M80s on one channel or something insane like that.

Well, you could solve the amplification problem, but to what end?

Front and center speakers are intended to present a coherent sonic image - to precisely place voices and instruments in space. QS8s are designed to diffuse sound into a broad area at the expense of imaging.

Plus, while Axiom design emphases response curve families (how speakers respond and measure off axis), it still optimizes frequency response to be nearer the speaker's axis.

So, you know, whatever you like, but there are design principles that indicate most people will be happier in the long term having tweeters pointed at their face.

Without a direct radiator type speaker for the center channel, it seems to me where it might be a bit more difficult on room correction, through ones receiver or pre/pro.

I wouldn't recommend using the QS4's as dual center channels. There would be major interference that would occur between the two speakers that would compromise timbre. They only play down to about 100hz as well. The QS4's to my ears have a different tonality/voicing that wouldn't match well to a front soundstage IMO.

Would there be any benefit to using more than one speaker for surrounds or presence?

I think that would depend on the size of your room and seating positions, multiple rows of seats would benefit from dual surrounds. I doubt presence speakers would benefit from multiple speaker layouts other than both height and wide at the same time in a very large room.

I was thinking of placing the one above the other powered seperately.
In theory if the lowest speaker was a foot or so below ear height and the second a foot or so above the results would be more natural envelopment.
I don't own any QS8's yet so I'm expecting some negativity.
Still thinking of ordering 2 pairs and running my surrounds in this manner. If it doesn't work I'll swap the QS4's to the back and throw the 2nd set up front as presence.

Don't know what "negativity" you might be expecting from that arrangement, but although it should certainly work, it would seem to be redundant. The QS8s have exceptional horizontal and vertical envelopment by design and it would be unnecessary to arrange two of them vertically.

I have read good things about them. I'm quite exited to make the call but it'll have to wait another month or two.
I am a fan of where surround technology is heading and thought it might be possible to get ATMOS type surround (similar not equivalent) from a typical 7.1 setup.

a few beers later it sounds like dumb idea.
when/if I try I'll report back. ;-)