I was thinking about how much space the on wall needs to be given so it doesn’t sound like it’s at the back of a bookcase.
If I made the QRD 8” deep that puts the VP180 drivers at 4” … so my first guess would be to give it at least 6” of space all the way around.

I’m assuming your thinking of the QRDs made of blocks and not the slat kind … also
This might be another use for Axiom’s packing foam … I’ll have to add that one to the packaging reuse thread smile