For what it's worth, and for those using OS 4 on any of their machines, the boot floppy has a version of scsi.device that is >52. I use this on all my classic machines.
Version >NIL: scsi.device 52
If Warn
LoadResident DEVS:A1200/scsi.device reboot quiet
EndIf
Suddenly, the second channel on the internal IDE adapter and other nice little benefits are usable on the system.