Like many, I have been frustrated by the current Font Size issue with EPUB books, and I find the "Standard" Kobo book format is not to my liking either, as there is too much wasted space in the margins. So this is what I do to get the ebook to format to match my desires....
- Remove the DRM if required
- Import the file into Calibre
- Ensure that the Calibre convert settings include "Justify" (about half way down the page on the right)
- Convert the ebook (this ensures that a .css file is actually in the structure as Adobe Digital editions doesn't seem to have a .css file)
- Remove the Style.css file one way or another (I found the single KoboEpubFixer program didn't actually remove the CSS file when that option was ticked, but the Bulk one does - just make sure you don't re-process previous files)
- RE-CONVERT the ebook once more (this is important as it creates a NEW .css file without font size, but maintains the justification for you)
It might seem like a long way around the problem, but I like the final format generated, as I think it is much easier to read than the standard Kobo format.
Cheers
John in Sunny Carnarvon - Westen Australia