I'm on Redhat based systems
There are 2 issues here are you trying to replace the boot kernel.... If yes then the kernel is squashfs filesystem which you may have to edit by putting the necessary librarys.
If all you want to do is replace the kernel that is currently being loaded then you can add in the
%post section of your install /usr/src/kernel/linux-2.6.x files (incase u want to tinker with the kernel later this is not recq) /lib/modules/2.6.x (this is what is recq) /boot/initrd-2.6.x.img (this is to boot) /boot/vmlinuz-2.6.23 (this is to boot) /boot/System.map-2.6.x (this is to boot)
Run a sed -i against /mnt/sysimage/boot/grub/grub.conf to insert your new kernel ie this has to be inserted as the first boot kernel.
title Fedora Core (2.6.x) root (hd0,0) # verify what this is on one system kernel /vmlinuz-2.6.x ro root=LABEL=/ rhgb quiet initrd /initrd-2.6.x.img
. and your done. do all this on a http install and start your systems with a pxeboot .... dd to about 10 systems will take a hell of a lot of time and thats the reason a ks file can be used and created.
Derwyn