How to disable HW compression in Tru64

In the AES ASAM thread I mentioned that we're being required to encrypt our data. Our current tape drives don't support HW encryption and we can't replace them so we're going to have to use the AES SW encryption. My concern is the time increase when EAS is enabled. Some of my test backups about doubled in elapsed time because compressasm doesn't work with AES.

Currently HW compression is turned on and I want to turn it off to see if it has an affect. So here's my configuration:

NetWorker V7.3.2 Build 399
NetWorker server: Red Hat Linux V3
NetWorker storage node: Tru64 V5.1B
Jukebox: HP MSL6060 with 4 Ultrium 460 tape drives.

There doesn't appear to be a way within the Jukebox or the tape drives to manually disable compression. I've been in contact with HP Support and they couldn't find a way. With Tru64 you control compression by device name. To enable compression the device name it's /dev/ntape/tape1_d1, to disable it it's /dev/ntape/tape1_d2.

Here's the problem. The 4 tape drives are already defined within NetWorker with compression enabled and I've never tried to define devices myself. This was done by someone else (no longer here of course).

I want to do just a test so can another device be manually added that disables compression and leave the device that has compression?
I have device /dev/ntape/tape1_d1 and I want to add /dev/ntape/tape1_d2. Would that mess things up? Or do I have to delete /dev/ntape/tape_d1? What are the steps?

I'm rather cautious because this backup server is for our mission-critical applications so I have to make sure that backups work.

Thanks,
Vic