Kevin,
Perhaps you missed my reply concerning an issue with splitting.
https://www.mobileread.com/forums/sh....php?p=4202498
As iOS books seems to require ID destinations for all TOC entries for EPUB 3 nav, I usually add an id to the body tag and add such destinations to the NAV. Such replacing also adds ids to the pagelist, as some publishers might not include all page numbers and for new chapters simply specify some xhtml file as first page number for a chapter. In such cases, splitting also changes the entry to the last split.