I've just run this setup with great effect on Fedora Core 6 which came pre-installed with my dedicated server. There were just two small things to note:

Before Step 4 (installing apache):

If you want to install a suPHP with ISPConfig later, you will need to install the apache2 header files otherwise compilation will fail. Run the following:

yum install httpd-devel

Step 6 (disabling the firewall):

The command in fc6 should be:

system-config-securitylevel-tui

I hope this helps somebody!

Neil Hamilton