I don't know where you got the idea that surround speakers in a 5.1.4 system would "look better" up high, but please dismiss that notion. You need as much vertical separation of the 5 bed level speakers from the ceiling mounted or in-ceiling speakers of the ".4" Atmos level speakers as possible.
You should have the 5 bed-level speakers all at ear level. The 6" to 9" from the wall should be OK, and you can use the port plug if they seem a little boomy. If you want to mount directly to a wall, the Q50a come with brackets already on them.
How big is the room and what spacing is there between the seats and a screen, and between seats and speakers? What are you using for center speaker, subwoofer, and AVR?
KEF R500, R200C, R100, R50, SVS SB2000 sub, NAD T758v3 AVR, Pro-Ject RPM1 TT w/ Ortofon 2M Red, Bluesound Vault2, LG UP875 4K BlueRay, Samsung UN55JU6500F 4K LED TV, KEF M500 headphones, Sony CDP-CE500 CD changer. Desktop: NAD M10, KEF LS50, KEF Kube 10b. Guest room: Hafler 200 L-R, KEF reference Model 100 center, KEF iQ10 surrounds, M&K V-90 sub.