USB storage pass-through for Hyper-V

Hi everyone, I have a 2012R2 hypervisor with two guests running on it. I need to be able to set up a pass-through connection of a Tandberg RDX drive to one of the guests. The hypervisor recognizes the drive but I cannot make it offline, to be able to add it to the VM.  When trying via diskpart It gives this error:

DISKPART> offline disk

Virtual Disk Service error:
The operation is not supported on removable media.

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Please note that this is the standalone hypervisor installation, not an app running on the standard server.

I've tried it with powershell to, using the below guide, but got a following error:
http://www.altaro.com/hyper-v/hyper-v-pass-through-disks/

PS C:\Users\mandel> Get-Disk -Number 1 | Set-Disk -IsOffline $true
Set-Disk : Not Supported
At line:1 char:22
+ Get-Disk -Number 1 | Set-Disk -IsOffline $true
+                      ~~~~~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : InvalidOperation: (StorageWMI:ROOT/Microsoft/...
   _StorageCmdlets) [Set-Disk], CimException
    + FullyQualifiedErrorId : StorageWMI 1,Set-Disk

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Any suggestions welcome.