A recent trip to Los Angeles resulted in a working 9885M drive and so I got back to work on the disk initialization project. The current version of Ansgar Kueckes' HPDir program allows you to create a 9885 disk on a 9895 drive with the incantation 'hpdir -initialize -9885 -s 9825 <msus>'. Once I realized that Ansgar's syntax added an extra zero to the msus (e.g. with my 9895 addressed as 7, the first drive is 7070: and the second drive is 7071:), I was able to [apparently] initialize a disk for my 9885 drive.
The 'apparently' part came when I hooked the 9885 drive up to my 9825A with the 98217A Disk ROM in place and attempted to access the drive. I heard contacts close and open in the drive cabinet as I powered the 9825 up and down but any attempt to use disk commands resulted in an 'error 03' - mnemonic unknown - on the 9825 console.
Is this a Catch-22? Do I still need the Disk System Cartridge (tape) to 'boot' the disk subsystem before new disk related commands become active? Or is it possible that my ROM is not being accessed?