In reply to an earlier speculation about why John Wetton's bass was in the middle speaker:
Wetton's bass cabinet was notoriously loud!!! So much so, that, playing live, they didn't even bother putting a dedicated mic or having a dedicated line going into the house mix. Since STARLESS AND BIBLE BLACK consisted of live recordings with later dubs, you would expect the bass in all the speakers. Given the choice, would you have it dispersed like that, or isolated to the subwoofers (and thus miss some of the higher ranges)?
I think not. The center speaker would be a logical place to put what you have isolated (with subs included, and tones coming from all speakers).
Wilson would be the one to know, though!