We're using 3 M5 units.  The main Deco currently connects to the two satellite Decos via wi-fi backhaul.

Things that I've read suggest that the antennas in the M5 are omnidirectional and the greatest signal strength is in a horizontal plane when the Decos sit on a flat surface (rather than wall mounting them).  Is this accurate, that most often* the Decos should remain in a horizontal orientation?  Is there a significant change if a Deco is ceiling mounted so that it maintains a horizontal orientation, but just inverted?

* I understand that physical layout, construction materials, etc. will all affect performance of a specific installation

Thanks,

Scott