the suggestions others provided may already solve your problem. but just fyi and for the benefit of the broad community. on 6k, the sys font usage is
( A ) Font meaning
meaning of the numberical value in the second place of the font name
normal helvetica_xxx_50
italic helvetica_xxx_50i
bold helvetica_xxx_75
bold+italic helvetica_xxx_75i
( B ) Sys Font
basically system only uses two fonts
1.helvetica_180_50_t10: for menus, tabs, settings, etc. This is the font you've seen most of the time.
2.helvetica_180_75_t10: for the fonts on the desktop and application subject (e.g. the site name or page name appears at the top of Opera)
note: Settings->Appearance->Font->use thick fonts is not selecting bold fonts. I guess it's using graphical methods to doulbe font appearance.
( C ) PIM
Fonts selection for the stock applications are built into the binary files in /usr/QtPalmtop.rom/*.so. The corresponding normal Font size in the PIM are:
minimum 120
small 140
medium 180 (default)
large 240
maximum 360
the default font size used to edit an entry in PIM is normal 240
you can find the sys fonts in /opt/QtPalmtop/lib/fonts. and now you can rename/relink them to fit your taste.
a more detailed discussion is in the china zug section where i try to display chinese font on 6k
https://www.oesf.org/forums/index.php?showtopic=9592