Unfortunately, option --disable-remove-fake-margins doesn't seem to work.
Yes, message about removing fake margins goes away but resulting azw3 (converted epub->azw3) still shows wide margins.
Fed the same ePub to kindlegen - and received mobi with decreased margins.
Using Sigil, set side margins in ePub to +20pt.
Kindlegen produced mobi with very wide margins.
Calibre again did nothing to azw3, no change to original margins.
I'm adding this code (plus or minus for sign of value) to css in my ePub:
Code:
* {
margin-left: 20pt;
margin-right: 20pt;
}
and applying option --disable-remove-fake-margins.
Maybe Calibre doesn't accept tag *?