Darn.
Since I'm doing installs day in day out I have a disk image of 10.5 on my server. Istead of sitting through a dvd install I just use the disk image and target mode to install either 10.4 or 10.5 onto macs.
Seems like while the installer runs fine under SL, in fact a bootable system is not created, even using disk utilities first to wipe the drive. Tried it with both 10.4 and 10.5 installs and both failed.
All the files install correctly but at the end you are left with a drive that will not boot.
Oh well back to using the dvds until I can find out why. Or booting my MBP from a 10.5 system on an external and then using the disk image to install.