There's a couple people here in this forum that have their Qs still as the lower surrounds in their systems with quite good success.
As from what I've read on Atmos. the height is the most important as a monopole. Due to the making of a "bubble" or a more vast prime listening seat. With the over heads directed towards the general area it supposedly can make a whole couch the prime zone.

I myself am still going from monopole to the Qs10 with my 7.1 finally!