OK thanks! Got the CD0 file in Devs -> DosDrivers, used Information to change the Unit# in CD0 to match the SCSI device ID. I'm a little unclear on checking for the presence of L:CDFilesystem. Where does/should that reside?
It could be in Storage: cant remember to be honest. It might already be in the L: folder.
Matt_H is right, apparently the built-in CBM solution is buggy, but it's a good start anyway.