Yet another update for the `Fix kepub side bearing font cut off bug` patch in
post #57.
I've added another patch that should work for sideloaded kepubs too, although it may work a bit differently on sideloaded than synced kepubs, and there might be some unwanted side-effects on sideloaded kepubs, so testing welcome.
Edit: Actually, I can think of a number of problems that will occur with sideloaded kepubs, and for some books they might be worse than the original problem. I think the only real solution (other than Kobo fixing the bug in the kepub reader) is to change Calibre to add the parts to the kepubs that it creates which are currently missing. (The book-columns and book-inner divs.)
Edit2: Updated patch again, this one should have fewer side effects on the layout of sideloaded kepubs.