Ok, some PROGRESS!
The 36 lb Spark Hanging Event!
Here's the back of the speaker:
Notice the amp takes up a significant amount of space on the back.
There is also no built in mounting hardware.
After discussing it with Mark Seaton in detail for a bit, I can screw into the back of the speaker. The backs/sides are 1.5 inches thick as the speakers are built like tanks.
With this in mind, I took these:
which are VESA wall plates for Monoprice TV mounts and attached them in place using industrial strength Velcro.
I used special non-tapering coarsely threaded 1.5 inch screws screwed through the mounting plate into the back of the speaker. I figured 8 per speaker would be plenty.
I think you could probably. There is no separating the plate from the speaker now! Very solid.
Pics of the finished mounting solution: