A great feature of xpostfacto is the possibility/necessity to use any disk supported in the early boot process as a helper disk and to boot afterwards into any other disk supported by this helper installation. You could use a little disk holding a tiny OS 9 installation with xpostfacto as a helper disk (for example the stock 4 GB or something like a small IDE flash disk) and afterwards boot into an internally or externally attached second disk (in case one expansion slot is occupied by a nice FW/IDE/SCSI host adapter card). This should bypass the 8 GB limit in the boot partition size as well as any disk performance throttle due to the cheap onboard IDE controller. Additionally, depressing the option key at boot time brings you always back to your classic OS 9 desktop