The back of the speaker is actually 12" from the wall. This is as far as I can go due to the room size. I haven't tried moving them any closer in or further away. You'll probably be fine with the front baffle 24" to 30" away. More is better but not always possible. Maybe Danny will chime in on this.
I first thought about an OB7 without the sub section; it would be the same width as the TV. That would put the woofers pretty close to the mains and I'm not sure how that would sound for home theater(although it would look awesome

). I'm no expert so if anyone has any thoughts on this I would appreciate it.
My current center is OK but it somtimes gets overpowered by the mains when there is dialog and music at the same time. Running it +4db sounds good but really I'm just itching for another speaker project

.
You're going to love your OB7s. They are a lot of work to build but the effort is worth it. If I were to do it all over again I think I would build them without the sub because I have an attic IB and don't really need the extra bass.