@keropi
Please re-read "slowly" what Crumb has written...
If you go and edit the Kicklayout-Axxx file (which you will find in your OS4/Kickstart drawer) to recognise your OS4 partition, it will not boot OS3.9 after the reboot. Instead it will immediately boot into OS4.
I'm still checking if i can find a way to boot OS4 without accessing the Early-Startup or disabling the Kickflash contents.
RTFM :-D
Alex