Well, I decided that I'll be doing the LFE channel over again essentially from scratch, so that's the thing I've been the most concerned about recently. I'm using the in-theatre recording as a rough guide, but it's still entirely subject to my creative judgement. The recording isn't a very reliable source, since it's filled with acoustic oddities and the fidelity isn't at all what I'd like, but it's enough to give a general idea what it should sound like, at least for the stronger parts.
This time I'm taking more care to ensure that the LFE is timed exactly right. Before I tended to get a little lazy about it when the synch discrepancies were small enough not to be noticed easily, but since I'm having another go it might as well be improved in that sense. I'm also re-evaluating some of my decisions about which source to use for each particular bass effect. The '97 mix is getting used even more often this time, since despite only having a lossy source the tonal quality of its bass is usually much more pleasing to my ear: the '93, though usually closer to the original, tends to be a bit thick and boomy when amplified, and the '04 is often toneless and dull.
I'm also making even more effort to ensure that the bass blends with the main channels. This can mean adjusting the timing to match, even after they've already been synched, and in some places I've split certain bass effects apart into segments and adjusted their volume levels individually (crossfading them back together to avoid jump-cuts). The reason for this is that sometimes getting a good average level will result in peaks that go too high, since the SE bass can correspond to additions that weren't in the original (and also I think they went a little nuts and pumped the bass too far where it wasn't needed, while neglecting the parts that do need a strong response.) Just for the heck of it, I also silenced all the gaps where the LFE isn't used in order to completely eliminate any noise in those parts, although that wouldn't really be noticeable anyway since the channel has an upper limit of 120 hz.
I have the LFE channels from the Bluray mixes, which theoretically would provide an improvement in sound quality in the places they're usable, but to be honest I haven't actually worked with them yet since I noticed that all the loudest bass is pushed up to the point of clipping. The peaks aren't chopped too horribly, so I doubt anyone would really notice, but I can't bring myself to put something like that in there, "lossless" or not. I can still use them in all the parts that aren't clipped, but it's annoying enough that I have not as of yet had the patience to do anything with them aside from converting to 16-bit.
Real life tends to kill my motivation lately, but I'd really like to get the new 70mm track done in the next couple weeks if possible. As I've said before, on the whole it will differ only subtly from the existing version, since I think I got it mostly right to begin with, but I'm pleased with what I've been able to do so far.