Fonts with non-standard sizes?

Hi,

I've made a morph which contains some text, and the font size should
depend on the size of the morph.

However, if I just try to set the font using
StrikeFont class>>familyName:pointSize: or TTCFont class>>family:size:, it only
gives me fonts in certain predefined sizes.

I know I can choose my own size using StrikeFont class>>fromUser, but
what's the best way to do this in my code, non-interactively?

Oh, and should I prefer TTCFont or StrikeFont, or does it not matter?

And what should I use for the font family, for maximum portability?
Can I assume BitstreamVeraSans is always available?  What's better
than assuming that?

cheers,
Simon