[OpenAFS] chown'ing and chgrp'ing user volume mount points

[Kevin]

Quick question if I could (sorry if it's a dumb one):

AFS UIDs are positive integers, right, and AFS GIDs are 
negative integers?  The guidance in the docs on 
creating new users with pts createuser and so forth 
has you chown the newly created mount point to the 
newly created AFS UID.  However, there's nothing on 
chgrp'ing that same mount point to be that of the main 
group that the new AFS user belongs to.  Should there 
be something along those lines?  And if so, how does 
one do it?  chgrp seems to check the local /etc/group 
file for defined groups (and fails when it's not 
there), and furthermore, trying to pass an argument 
that begins with a hyphen to the chgrp command is not 
straightforward to me:

chgrp -500 /afs/.folkvang.org/usr/user1

Doesn't fly.  I even tried escaping the hyphen with a 
\- and '-' and "-" but still no go.  How do I do this?

TIA.

-Kevin