The hole in the middle effect can be overcome with some speaker toe-in, at least that has been my experience.

The equilateral triangle is a rule of thumb and the width of the speakers should be adjusted for the best sound in that room. I would try running the speakers on stands of some sort before you wall mount them to give yourself the best idea of how wide you want to place them. Are you using the FMB to mount them with? If so, you can achiee a little toe-in with those mounts.


Jason
M80 v2
VP160 v3
QS8 v2
PB13 Ultra
Denon 3808
Samsung 85" Q70