In the .kobo/Kobo directory there's a
Kobo eReader.conf file which contains the Reading section. I've played with advanced settings for Amasis & Literata and I have this:
Code:
readingFontSharpness\Amasis=0.146666666666667
readingFontSharpness\Literata=0.0766666666666667
readingFontWeight\Amasis=0.64
readingFontWeight\Literata=0.43