Whoops! How time flies. Sorry you had to wait so long for a reply --
you've probably already given up or figured it out by now.
Anyway, I thought I had written something on this, but I looked around
and couldn't find it, so I wrote a new Wiki page on it:
http://code.google.com/p/slack/wiki/Subroles
It's actually really simple, but somehow the page ended up really long. :/
Let me know what you think, all.
--Alan