Right way to load hyphenation patterns

[Ville Voipio <ville.voipio@kpatents.com>]

I want to use a non-standard hyphenation pattern (Finnish)
in some of my documents. I have been able to make it work
by:

  editing cont-usr.tex (removing a % from the \installlanguage)
  remaking formats (texexec --make)
  copying the format wile to the .../web2c directory

This works. However, I read in the Wiki that "It is generally 
better to add local settings to a run-time included file like 
cont-sys.tex instead, so unless your stuff does absolutely 
have to become part of the format file, you are better off 
leaving this file well alone."

So, where should I put the \installlanguage directive for
it to be in the right place? Is it something that really has
to be there when the formats are being built, or could it
be loaded afterwards (i.e. at run-time)? Could it be put in
the cont-sys.tex?

TIA,

- Ville