In that room, I’d suggest setting up your Mirages along a diagonal (like you room is a diamond instead of a square). This will geometrically delay the arrival of the first reflections. If the reflections from the rear-firing drivers arrives too soon, they will degrade clarity. But delay their arrival for long enough (10 milliseconds is a good target) and they will enhance timbre and envelopment with little or no degradation of clarity... in fact you may even find that clarity is improved.
Duke