I've updated the `Fix kepub full-screen mode side bearing cut-off bug` patch in
post #57.
It now adds padding in units of 0.1em (with an alternative for units of 1%) to div#book-inner, and is a bit more compact.
It only works with synced kepubs, but another patch that works with sideloaded kepubs too might be possible.
I am using the patch myself, but I mainly just use the Georgia font. If you use different fonts and find that characters are still cut off, try increasing the amount of padding from 0.1em to 0.2em or more.