Probably font encoder have to be changed from ISO-8859-1-> ISO-8859-15, but how?
Xorg docs are old, very old.
If those Xorg -docs are concurrent, new configuration should be done from xsession -file, I think.
Modern way would be just to set LANG variable:
export LANG="fi_FI@euro ISO-8859-15"
How this should do for TC?