[texhax] Changing Font Spacing

[Karl Berry]

    Is there some command I can insert in the font definition file, like the 
    scaling factor, to get a narrower space between the letters?

Not that I can think of.  Perhaps one of the letterspacing packages will
do what you want.  (Assuming you really want it :)
http://www.tex.ac.uk/cgi-bin/texfaq2html?label=letterspace

It's possible to change the word spacing via assignments to \spaceskip
(and \xspaceskip), \fontdimenNNN, etc., but not letter spacing.

Best,
karl