HAHAHAHAH ...
It's finally done and all in sync.
When I said I was guessing, looking at it and saying, well, it goes out of sync at the dual layer break point, and I think (only from looking at it) it's by 7 frames ...
I was completely right. It WAS seven frames. (I've got a good eye, don't I?) The resulting version stayed in sync throughout.
I will still watch it a few times at the parts I don't usually watch it, to see if it goes horribly out of sync anywhere ... but I think it's DONE.
I will start burning copies rightaway.