I know several people have inquired about how to set up GFS on FC4. I have composed a howto which explains how to take a system running FC4 and get it to work with GFS.
It took me a while to find everything which needs to be installed, ports unblocked, etc, but the howto is actually pretty short, it almost fits on one screen. It only took me about an hour to take a system from no OS to joining a cluster.
check out: http://www.ethanet.com/FC4GFS/
send any questions to firstname.lastname@example.org