Testing addons....

I guess you need to use a tool which can edit existing iso images. Making a new one is not easy as we use mkzftree, and some parts of the cd should not be compressed (/boot). But you can try without compression:

Code:
 mkisofs -R -iso-level 4 -z -V "PVE" -o pve-cd.iso -b boot/isolinux/isolinux.bin -c boot/isolinux/boot.cat -no-emul-boot -boot-load-size 4 -boot-info-table data