I saw one of the screening in New York (1982?), along with orchestra, at
Radio City Music Hall, and would think only 3 screens were used.  I'm not
sure what 6 screens (as distinct visual fields) would look like.  The last
part of the film is constructed as a tryptich and (as I recall) was filmed
using 3 cameras--sometimes it forms one panorama and sometimes the two
outside screens form a commentary or counterpoint to the center one.  The
video version gives an accurate picture of what this performance looked
like (except not at size).  It is a great film, and the first appearance
of the expanded screen/image brought cheers.
                Jesse Kalin, Vassar College