LB cab issues

I talked to the seller, who has the same cabinet as me, and he said that he hung the 6-slot MVS main board on the back wall of the cabinet. That truly surprises me, as the back wall isn't even vertical, it's like an overhang. So the main board would be hanging at an angle, almost a bit upside down.

What's even more confusing is that this is obviously a cabinet meant for the MVS system, but it only has one speaker. How that is supposed to work with the stereo output of MVS is beyond me.