[Fontinst] letterspacing with fontinst

[Ingo Reich]

Hi everybody,
I've got a font that is set a little bit too narrow (in my opinion). 
Playing a little bit around with sout.sty, I found out that the font in 
question (Foundry Sans) looks much better if the letterspacing is 
increased by 0.015em. Now my question is: Does anybody know a simple 
way to increase letterspacing with fontinst? (Maybe a *general* way to 
change kerning information?)
Any hints very much appreciated.
Best, Ingo