I just tried the following kickstart settings when provisioning RH AS 4, and it seemed to work really well! (no need for post install script to turn of iptables).
firewall --medium --trust eth0 --ssh --port 4750:tcp
If you are brave, then you can turn off ssh as well!
the following also works for functionally disabling the firewall during the post os install script phase of the kickstart file:
-- METHOD 1, THE BRUTE FORCE WAY --
Mv /etc/rc3.d/s##iptables k##iptables
Mv /etc/rc5.d/s##iptables k##iptables
-- METHOD 2 --
firewall --trust eth0
-- METHOD 3 --
chkconfig --del iptables