As this is the PRS+ thread,
you can change system fonts even without flashing them!
At every startup - w/o connected USB - "prsp.sh" in /Data/database/system/PRSPlus is called.
There you can place some code like this:
Code:
cp /Data/<ANYFONT.ttf> /tmp
mount --bind /tmp/<ANYFONT.ttf> /opt/sony/ebook/FONT/tt0011m_.ttf
Replace <ANYFONT.ttf> with your font and place this font in the root of IM (AKA /Data/)
The font had to be prepared to meet some requirements, best with pepaks tool
here