HD Problems with Tru64 Server / AS 8200

Hello Admin Wizards,

one remaining problem:

The AS 8200 has optional internal HDs - up to four on the back and one 
on the front side, just beside the TLSB Cage.

I received the system with one HD in the uppermost slot on the backside 
and the CDR. They are connected to ISP3 and show up if I issue a show 
dev at the SRM prompt like that:

pkd.7.0.5.0 (the termination I suppose)
dkd0.0.0.5.0 (the RZ28 HD)
dkd400.4.0.5.0 (the CDR)

Now I supposed that if I inserted other RZ28 HDs in the remaining free 
slots they should show up like that:
dkd1.1.0.5.0
or something like that. But they dont; in fact, the do not show up at all.

Installing Tru64 5.1b was a breeze, and the system works perfectly - but 
I would really prefer to have a backup for my bootdisk (I planned to do 
  a dd once the other identical disks are recognized).

Any hint would be appreciated.

Thanks a lot
CW