This is the best picture I could find in a few minutes of searching:
http://www.flickr.com/photos/2242118...7611844292070/
The drawings should say how far back in relation to the wall, but I haven't had a chance to look at them all yet.
When I do, & if I find out, or can calculate that distance by drawing everything up, I'll get back to this thread.
Also:
http://www.thesixweeks.com/images/kickoff16.jpg
Judging by the size of the ball in relation to the arm of the seat (bottom right black part), it would
seem to be about 2-3 ball lengths away, or about 20-30" away.
But that is a gross estimate of a guess here.