Drive type

[Ayman Altounji]

I am using an internal DLT7000 and an external DLT8000 on the same server, under Veritas' backupexec 8.5. This software will not allow me to create a cascaded drive pool because the software recognizes the two drives as different drive types;

DLT7000: DLT64K (64K,10,0,GU)
DLT8000: DLT32K (32K,10,0,GU)

What, can I do to make the software see the drives as the same type?
Is it a hardware or driver issue?
If this is not possible, why is this incompatibility not noted in the literature?