hi
I tried Jellby's method previously (as described by Katsunami) but I generated a huge and unusable font. Fontforge reported lots of mistakes but complied. On the other hand, JSWolf succeeded very nicely to embolden Charis Sil (modified and compact) but I don't know if he used Fontforge or another tool.
According to Katsunami, one may have to try several times, guessing any value between +50 to +75. It's very much a trial and error process.
As Kobo is allowing side-loaded fonts, my idea was, as you try to do for Fontin, to embolden just a bit Linux Libertine OTF (v. 5.3).
http://sourceforge.net/projects/linu...bertine/5.3.0/
I noticed that the Kobo Patcher allows me to embolden very precisely any side-loaded font including this one but up to now this works only for regular fonts because italic font is displayed as bold... (a Kobo bug?) so I am still loooking for a solution à la JSWolf because Charis Sil modified emboldened italics are properly displayed.