Glad to hear you made progress despite me getting distracted! 
So with what you did it’s not performing a backup? It so and you have the time/resources, please let us know if a restored VM works as expected for you.
I’d love to use your steps as they basis of a #howto guide!
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General question for all Hyper-V Duplicati users… Have any of you backed up a Hyper-V VM with a passthrough (physical) drive?
There’s a Microsoft page about Hyper-V backups that mentions their tool won’t back up passthrough devices at the host level…