Make a full ISO Tips

Can you help me with some tips to make distro a full ISO without netinstall. We use this great version for many customers and we want to wait before using the newer versions. I think I have to get the adjusted Centos 5.5 kernel with some adjustments in the install script, so that the iso fetches the files from the local cd-ISO.
I hope you can give me some tips before I start building an ISO.
Many thanx in advance

Well I can tell you it tooks weeks for us to setup the Full ISO building so its not a trivial thing. Also remember our kickstarts are copyrighted so you would not be able to use those.

The problem is that version has a buggy Asterisk with security exploits and a unsupported FreePBX version so not sure why you are trying to use that still.

Thanx for the answer Tony.
What would be the best version now to upgrade to?
The latest with asterisk 1.8 1.815.210.58-1 or the new asterisk 10?
Asterisk 10 is no LTS version, so that gave me some doubts. Maybe I am worrying for nothing?