Someone else pointed out my error in thinking that only the NCX controlled order.
in the
content.opf the spine section comes into play
Code:
<spine toc="ncx">
<itemref idref="titlepage.xhtml"/>
<itemref idref="books.html"/>
<itemref idref="copy.xhtml"/>
<itemref idref="map1.xhtml"/>
<itemref idref="map2.html"/>
<itemref idref="map3.html"/>
<itemref idref="pro.html"/>
<itemref idref="p01.html"/>
<itemref idref="c01.html"/>
</spine>
Validate the EPUB with Flightcrew (also part of Sigil). fix any syntax errors, then carefully adjust the spine order.