1. I went back to the epub2 file, deleted the cover html file, and added it with the [Add Cover] menu
So somehow I must have messed it up -- all I ever do intentionally is use the menu
epub2 --
Code:
<svg xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" version="1.1" width="100%" height="100%" viewBox="0 0 306 423" preserveAspectRatio="xMidYMid meet">
<image width="306" height="423" xlink:href="../cover.jpg"/>
</svg>
so at least the image is not distorted
2. The image size seems to have changed
After I deleted the cover html, re-added the cover, and upgraded to epub3 the image is much smaller
epub3b --
Code:
<svg xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" version="1.1" width="100%" height="100%" viewBox="0 0 306 423" preserveAspectRatio="xMidYMid meet">
<image width="306" height="423" xlink:href="../cover.jpg"/>
</svg>