Help needed cloning XBOX HDD with dock

I've got a Vantec dual bay HDD dock that can do 1:1 copies... or so I thought. I did a copy of a loaded 2TB from one newly loaded WD Blue to a matching brand new WD 2TB Blue. The cloning process completed, but when I put the new drive into my XBOX there is no F or G partitions, F is empty and G is path not found. The first drive was setup on FatXplorer, and works like a dream. Any suggestions?