Thanks, guys! This is a great technique with lots of uses. I love re-inventing the wheel -- it forces one to learn it's nuts & bolts ... so you can screw everything up in novel ways (and that's mostly a good thing)!

For example, the resulting frame of this proof-of-concept shows an "apparent" fringing of red in some areas. (I hope that was not being referenced as the "registration" problem. The film scan itself does have fringing from chromatic aberration, but that is from the scanning equipment -- see this thread's page 52). This HSL-recombination "fringing" is actually damaged coloring in the DVD, courtesy of GL and company, which used this occasion to surface (an easy fix, though).

Notice in the DVD H-S-L split that saturation "hits the roof" (white) in small, particular areas. Back to the resulting frame, those very same areas glow (red in this case). Yet the 16mm scan, even with it's film fade, does not have any corresponding spike in saturation in those (shadowed) areas.

Alas, Lucas Film is everyone's whipping boy ... but for good reason. And, thereby, we have our work cutout for us. :)