I've updated the first post of the thread to contain the links for the 'purist' mixes as well as giving more accurate descriptions.
Thinking back, I'm remembering how this all started with me being bored one day and taking my 2004 ESB dvd into a high-end home theatre store, and being amazed at how powerful it sounded with a real LFE channel. Ever since then I wanted to be able to watch the movies with that kind of strong bass but without having to see the SE changes or the horrid blue-cast, so once I got myself a good subwoofer I set about trying to make that happen. It took a while to figure out, and a lot of close listening before I knew for sure what they should really sound like, but once I learned that Star Wars was actually the first movie to use LFE in the modern sense, I knew my effort was justified, and that using it for a 70mm recreation would be a worthy goal.
So, just for fun, here's a list of everything in my 70mm LFE channel, including the time, a description, and what was done to make it fit into the rest of the soundtrack. The majority of the bass in the first movie came from the 1997 special edition 5.1, which plays back with an average volume four decibels lower than the 1993 mix, so all level adjustments for '97 bass are relative to this difference, while the 2004 content did not need to be adjusted this way. The 1993 effects gain (I believe) another 3 db over what I've listed when combined during playback with what is in the main channels, and are relative to the LFE channel needing to be recorded 10 db lower.
2'10: blockade runner appears; '97, +6 db
2'14 - 2'27: Star Destroyer rumble; '97, +8 db
2'34: blockade runner hit; '97, extended beginning to match synch
2'47: reactor shutdown; '97, +2 db
3'19: ship pulled into hangar bay; '97, -1 db
3'39 - 3'47: stormtroopers blast through wall; '97, +4 db, faded in beginning to match main channels
4'27: laser impact; '97, +6 db
4'33 - 4'52: Vader appears; '04
6'54: laser impact; '97, -1 db
7'02: escape pod launch; '04, +4 db
8'51: Star Destroyer; '97
12'24: R2 falls; '04, -12 db
15'00: sandcrawler; '04, +4 db
15'23: sandcrawler; '04, partially duplicated from previous effect at lower level
36'33: Star Destroyer approaches Death Star; '97
38'13 - 38'28: Force choke; '97, +2 db, ended slightly early for better blend with main channels
41'16: cell door slams; '97, +2 db
50'21: Death Star; '97
53'10: Millennium Falcon takeoff; '93, +4 db, phase-inverted to sum correctly with upmixed main channels
53'20: Falcon flyby; '93, same
53'35: Falcon flyby, Star Destroyers; '93, same
53'56: Star Destroyer fires; '93, same
54'29: jump to lightspeed; '93, same
54'30: Death Star approaches Alderaan; '97, -4 db
56'40: Alderaan destroyed; '97, first half +2 db, SE shockwave -8 db, bass extended until end of shot, very beginning shortened to blend with main channels
1:00'41: hyperspace; '97, +2 db
1:00'49 - 1:01'09: planetary debris; '97, +2 db, last two impacts added to match main channels by duplicating from earlier
1:01'21: TIE fighter flyby; '97
1:01'29: Millennium Falcon flyby; '04
1:01'39: Falcon flyby; '04, -5 db, synch adjusted to match main channels
1:01'53: Falcon flyby; '04, -5 db, synch adjusted to match main channels
1:02'15 - 1:02'40: caught in tractor beam; '93 for 60 hz tone, '04 for 40 hz tone, +3 db
1:03'06: approaching Death Star; '04, +3 db
1:14'49: stormtroopers destroy door; '04, -6 db, synch adjusted to match main channels
1:15'55: Leia blasts garbage chute; '04, -6 db
1:17'20: trash monster roars; '04
1:19'17 - 1:19'45: walls close; '97, -4 db
1:20'38 - 1:22'06: walls close; '04, faded out ending to blend with main channels
1:25'36: chasm door slams; '04, +2 db
1:27'25: blast doors close; '97, +2 db
1:27'43 - 1:27'59: Vader appears; '97, -6 db
1:30'44: Millennium Falcon takeoff; '04
1:30'56: Falcon flyby; '97, +2 db
1:31'15: Falcon flyby; '97, -4 db
1:31'56 - 1:32'04: explosions (x3); '04, first one +3 db
1:32'31: Falcon hit by laserfire; '97, +2 db
1:32'56 - 1:33'40: TIE fighter explosions (x4); '04, +3 db
1:33'52: Falcon flyby; '04, -6 db
1:35'37 - 1:35'56: Millennium Falcon approaches Yavin (x4); '97, -1 db, -2 db, -1 db, no change
1:36'46: Death Star approaches Yavin; '04, -4 db
1:38'33: Death Star approaches Yavin, '04
1:41'32 - 1:42'02: fighters prepare for takeoff; '97
1:43'02: fighters approach Death Star; '97, +2 db
1:43'23 - 1:43'36: X-wings attack, '97
1:43'40: turbolasers; '04, +2 db
1:43'50: Luke attacks; '04, +2 db
1:43'59: X-wing flyby; '97, ended early to blend with main channels
1:44'24: Biggs and Porkins attack; '97/'04, +2 db
1:44'35: Porkins explodes; '04, +4 db
1:44'51: Luke attacks; '04, +2 db
1:45'18: TIE fighter destroys X-wing; '04
1:45'37: Luke destroys TIE fighter; '97, +2 db
1:46'28: Wedge destroys TIE fighter; '97
1:46'51: Y-wings enter trench; '97
1:47'03: turbolasers; '97
1:47'47: Y-wing explodes; '04, +3 db
1:48'01: Y-wing explodes; '04, +3 db
1:48'09: Y-wing explodes; '04
1:48'48: X-wings approach trench; '97, -2 db
1:48'58: turbolasers; '97
1:49'01: X-wing flyby; '97
1:49'18: X-wing flyby; '97
1:49'28: TIE fighter flyby; '97, -4 db
1:49'38: X-wing explodes; '97 +1 db
1:49'48: X-wing explodes; '97, +1 db
1:49'55: proton torpedo detonation; '97
1:50'30: Red Leader crashes; '97, +2 db
1:50'46: X-wing flyby; '97
1:50'56: Luke enters trench; '97
1:51'06: turbolasers; '97, +2 db
1:51'27: turbolasers; '97, +2 db
1:52'14: Biggs destroyed; '04
1:52'25: X-wing flyby; '97, -1 db
1:53'53: Millennium Falcon destroys TIE fighter; '93, +5 db, phase-inverted to sum correctly with upmixed main channels
1:53'58: Falcon flyby; '97
1:54'02: TIE fighter crashes into trench; '04
1:54'05: Falcon flyby; '04, -10 db
1:54'19: ships fly away from Death Star; '97
1:54'23: Death Star destroyed; '97, +2 db, faded out before SE shockwave
1:54'48: ships return to Yavin; '97
Empire and Jedi were pretty much the same sort of thing, except much less work because they were better mixed to begin with; the 2004 LFE was used exclusively, but these were nearly the same as the 1997 anyway. I put together new bass in a couple of places in Empire, namely during the snow battle and when the Falcon faces the Avenger, and made a general effort to restrain excessive peaks, bring up parts that needed bolstering, and improve synch as needed; but compared to the first movie they were hardly changed at all.
It's all a bit obsessive, I suppose, but I think the end results speak for themselves. ;)