I don't see how that makes a difference, since in the LEFT position, the sound will be coming right over the listener's head, almost certainly defeating the other speaker. Surround should be diffused anyway, and not pointed directly at the listeners. Moving the chair or chairs on the left to be...
The orientation you show will give you absolutely no rear separation and will sound like one left speaker. I'd agree with putting one on the opposite wall, or mounting both on the ceiling. Ceiling will give you the most flexibility, but wall mounting will give you more separation. I'd leave...