@Diapdealer: Stories is still a good old mobi7 (and that's a shame, especially for Joe Hill's short, but I digress), and Blackbirds is a mobi8 (non-combo) built by Calibre from an ePub, but I think I remember seeing a working nested NCX on mobi7 books, too.
EDIT: Yep, nested NCX on mobi7, too (and that's from stuff straight from my Archive, so it's not just Calibre/Kindlegen magic ^^)
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