I just spent a day try to get openSUSE11.0 to load some custom iptables settings in conjunction with the SUSEfirewall at boot. I've got it working now so I thought I'd share:
1. forget about trying to set up a script to run like a service with chkconfig. It just won't work (even with S99!). I suspect the firewall flushes the settings later, after these rc.d scripts are executed, it's not clear how or why the settings get ignored but trust me - they will be ignored.
2. You'll need to edit /etc/sysconfig/scripts/SuSEfirewall2-custom. Put the custom iptables commands where appropriate, details are given in the file itself. Do read what is in the file because there is no man page for this.
What I wanted this for was to get postfix to listen on another port as well as 25. Fiddling with postfix itself can produce an open relay and so is not advised. A more elegant solution is to use iptables with the following command:
iptables -t nat -A PREROUTING -p tcp --dport 1025 -j REDIRECT --to-ports 25
The three steps above show how I got the custom port mapping rule to auto load at boot. If you don't follow the steps then the settings are lost on reboot - a common complaint.