Are you sure that there are "larger fonts" available on your system? Can you see them using a non-perl tool?

What does the man() page say about retrieving fonts? Particularly what is supposed to happen if you request a non-existant font?

What kind of "crashes" are you seeing? And where -- in Perl? Or in the Xosd library? Or elsewhere.

As is usual with The Oracles, the more precisely you can define your question, the more likely the Answer is going to help.