[racket] scribble/sigplan question

Hi!

I'm producing a scribble/sigplan camera-ready paper, and can't get the
copyright text quite right.

I got different copyright text from the publisher than what's included
with Scribble in collects/scribble/sigplan/sigplanconf.cls for the
definition of \permission.  I can modify the .cls file in my checkout
of Racket myself, but I'm wondering if there's a better way to do
this.

Is it possible to configure which sigplanconf.cls I use, change what
\permission uses for text inside my scrbl file, or do something else
more re-usable than modifying the checkout?  I think I just lack to
Scribble-fu to know what to try.

Thanks!
Joe P.