There is an issue with
spreads when authoring KFX with Kindle Create and then converting to ePup using From KFX: the <itemref> for spread pages have no properties attribute, so they get rendered (and squished) onto a single page rather than spread across two (I'm testing with Thorium Reader).
So for example:
<itemref idref="part0067.xhtml"/>
should be
Code:
<itemref idref="part0067.xhtml" properties="rendition:page-spread-center"/>
I have not seen this when converting KFX to ePub with one downloaded by Kindle for Windows; the required property is set. AFAICT there is nothing I can set in Kindle Create to control this (the page is marked as 'single page' instead of 'facing page').
I tried using the same properties value for the cover page, so it is centered, and I think that looks better than having it to one side or the other in 2-page view. It's how Kindle Create previewer shows it, as well as any other pages marked as 'single page'. (I do not know if there is a more semantically correct value to use for this, but at least this one seems to work.)