Are you asking about having the svg-files directly in spine?
Or whether to add the svg to the html file as a file or as xml (with the <svg> tags)?
I have had good results with adding svg as images in the html files, inside svg tags (yes it's hacky)- it seems to be supported on most reader systems (e.g. ADE3 - I ignore ADE 4 as it was so bad in the beginning - but it might have become better). It also works when converting to kindle.
Example:
html (Side_02.html):
Code:
<div>
<svg xmlns="http://www.w3.org/2000/svg" height="100%" preserveAspectRatio="xMidYMin" version="1.1" viewBox="0 0 203 297" width="100%" xmlns:xlink="http://www.w3.org/1999/xlink">
<image height="297" width="203" xlink:href="../Images/02a.svg"/>
</svg>
</div>
Make sure that the viewbox size and the image height + width are the same.
It is a bit of a hack, but it has worked consistently with many different titles - I have mostly used it for faking fixed format poetry in dynamic ebooks.
opf:
Code:
<item href="Text/Side_02.html" id="Side_02.html" media-type="application/xhtml+xml" properties="svg"/>
<item href="Images/02a.svg" id="x02a.svg" media-type="image/svg+xml" />