I've had to resort to a second pass through the data to count offsets, and that's now working reliably. I've also got the reconstitution of hyphenated words at linebreaks working, but only most of the time; for some reason, when the linebreak precedes a <fw> element, the reconstitution fails. I'm still working on that, but it's very mysterious. I'll probably have to create some test data rather than working on real files until I get it sorted out.

All in all, though, very promising progress.