Originally Posted by NiLuJe
The latest versions of the Fonts Hack do support tweaking the fonts in KF8 files
Are you talking about the hack described here?
Am I right in understanding that there's no way to accomplish what I want without modifying the firmware? I liked that the old trick I used just required modifying a text file and copying the font files into the right place.
But, before you embark on that path, you might want to check the styling of your book, there's a 'feature' (hint: it worked fine on older KF8 renderer (Touch)) where some font* styling directives are followed, even when they're stupid, preventing the Kindle from switching fonts, and falling back to the default system sans/sans-serif/mono families. (A quick search here & in the mobi forum might reveal more details about that, I never bothered to try to fix it myself, but I do have several books displaying this behavior ).
That shouldn't be the issue in the books I've tested so far as I customized the styling for those and didn't include any font directions. The only way it could have happened is if calibre added font stylings when converting from epub to azw3.