The built-in recipe for "The Economist" generates a title page so that the cover image is disproportionately stretched in some programs and readers. The resulting html-script of titlepage.xhtml contains the following code:
<svg xmlns="http://www.w3.org/2000/svg" height="100%" preserveAspectRatio="none"
To fix this issue:
p.s. and maybe to do same thing for other recipes to preserve cover image proportions?