hairy_hen: Thanks very much for the detailed reply to my questions. :)
Sounds like the 70mm stereo mix restoration is about as close as it can be to being just that, the 70mm theatrical soundtrack down-mixed to stereo, with nothing else added (DC changes removed). In this case, that means 99% (or whatever the number is) DC soundtrack.
Too bad about the 1997 SE laserdisk 5.1 soundtrack. They had a chance to bring the 70mm theatrical soundtrack to laserdisk in a rather hi-fi way (have to love PCM) and they didn't do it. Plus, from your description, they also introduced problems that weren't there in the theatrical soundtrack (reminds one of lots of things in the SE that they never should have done). I've always like the 1993 Definitve Collection soundtrack in terms of it's overall quality, smoothness and power, and apparently your examination of it compared to the 97 SE bears this out. Considering there is no separate LFE channel, it's really quite impressive. :) Plus, as you said, it's much closer to the real 70mm soundtrack (tinny sound introduced in the 97 SE is definitely something we don't want with non-SE video). And after seeing the reasons behind it, I agree completely with using the DC soundtrack as the main source for the 70mm 5.1 soundtrack recreation. :)
Also, I'm glad to see that you were so careful to check all available Star Wars soundtracks and personal reports when deciding what the most correct level should be for the bass in the LFE channel in various scenes. Since the goal is not so much to make it sound subjectively "better", but rather to restore the bass level to be as accurate to how it was in theaters as possible. Which, of course, also makes it sound better, since it was powerful to begin with. :)
Were you able to totally eliminate those phase cancellation issues that you mentioned? Were you able to remove the added-in LFE related to the CGI stuff added to the SE video (that is obviously not present in the GOUT video being used) and still keep it seamless (by maybe using bass from the 93 DC to make the sounds and SPL levels correct for those parts of those scenes)?
I noticed you mentioned that Return of the Jedi is apparently already done. Is this because you've already done the 70mm stereo and 5.1 restoration mixes for it about as well as it can be done (i.e., to the standard of the recently finished Star Wars)? Was Return of the Jedi done first because it was easier to restore?