I went with on-wall M3s and then used Axiom Full Metal Brackets for the fronts (that needed more angle) and just made a small "wedge" out of a 2x4 for the rears since they didn't need as strong of an angle. Just remove the woofer, and use screws to attach the the wedge (once the wedge is attached to the ceiling of course)...

The rears are fairly low profile this way.

Just a thought.

Farewell - June 4, 2020