SCSI has no concept of "slave," so that won't work. You *must* have unique IDs for devices on the bus, or badness will occur.
In your PM re: Sunrise, you mentioned that you had no system folder. That may be why you had problems. System 6 doesn't formally allow the system file to reside on the desktop. What you think is there is actually an alias. Sunrise may not have been written to figure that out (it is only 20K bytes or so!). I have no trouble with Sunrise on my Plus running 6.0.8 with the same CD drive as yours, the CD300e. Barring any Plus-vs.-SE issues, the major difference is that I do have a system folder, in which resides System, Finder and the driver.
But all that's irrelevant, since 5.3.1 did the trick for you. But in case you run into other odd behaviors, I recommend creating a system folder. It doesn't have to be named anything special (even "nofolder" works as a name), but I do recommend a folder of some sort in which you place the system file and associated bytes.