Originally Posted by charles_cinci
I do have on request, rather than just copy/not copy the existing cover, how about a way to tag an existing section other than the one named "Cover" as the section to use as the cover of the split off epub?
Epub covers are, unfortunately, not all that straight forward. Some readers require certain file naming conventions, metadata setting, only jpgs, etc. It's a bunch of extra functionality that already exists in other places that I'd rather not reinvent or appropriate.
I would suggest that you include the sub-covers as the first section of each split book, then use calibre's built-in 'set cover from ebook' feature followed by the Modify Epub plugin's 'Insert or replace cover' feature. Both of these can be done on batches of books at once.