Create custom iso EL6U4

Hi,
   I wanted to add some extra rpms including kernel rpms to the existing ISO image, followed the below procedure:

1. Create a directory to mount the iso.
   mkdir /tmp/bootiso.
2. Loop mount the source ISO which I'm modifying (EL6U4)
   mount -o loop /path/to/some.iso /tmp/bootiso
3. Created a working directory for customized media.
   mkdir /tmp/bootisoks
4. Copied the source media to the working directory.
   cp -r /tmp/bootiso/* /tmp/bootisoks/
5. Unmount the source ISO and remove the directory.
   umount /tmp/bootiso && rmdir /tmp/bootiso.
6. Change permissions on the working directory.
   chmod -R u+w /tmp/bootisoks
7. Copy your Kickstart script which has been modified for the packages and %post to the working directory.