Another thing to consider about the IMAX version is that there may have been some pan-and-scan shots in the film as well. Jim Ward says in this article here that they used the pan-and-scan DVD for reference when creating the IMAX edit.
It's funny how in hindsight now we see how important it would have been to make a recording of this version. If it was playing at IMAX *right now*, I'm sure some of us would be making special trips to see it just to get a camcorder copy for reference.
--SKot