I spoke to Mr. Price and this is what he told me (which is either those most or least trustworthy information as these things go . . .)
There is a seven minute version, a 13 minute version, an 18 minute version, and a few (9?) 20+minute versions. Within those last ones there are enough differences that Price says they are different (some greater than others--for example the print Canyon has at one point had its sound track erased and when he had it to relay this he made additional changes).
More differences arise in the sound--every cut he makes on the prints causes a crash in the sound track, which I think functions differently, or at least to a greater degree than the tweaking. In addition to the sound that was on the original print there are silent prints that have a cassette tape with them--the A side is the Gregorian chant stuff plus witches from a halloween tape. The B side is the same information, backwards, with more tweaking.
There are two prints that are almost exactly the same in sequence that Mr. Price shows as a double projection. He says the difference in these is great enough that he knows which one belongs on the left and which on the right.
13 May 1999