cvs permissioning question

I've just set up CVS on Linux, the problem I'm having is
that when people write files to CVS via Eclipse, the file
permissions on the unix side are set improperly:

-r--r--r-- 1 ian cvs 203 Nov 23 14:08 rob.test,v


I'd like to set this such that any user who is a member of the
cvs group would add files with 664 permissioning. I checked
the UMASK on both the CVS account and the IAN account
and it's set to 0002 on both. Just wondering what I'm missing
here. Thanks!