I'm posting this in hopes that it will help someone else. If your just using it to transfer, you can get a 4TB mybook and do what I did below.
Then when your done, you can format it back to a 4TB NTSF drive for whatever. (google for instructions to get it back to normal)
I have a 4TB WD Mybook. I plugged it in and it formatted on the receiver fine, but it wouldn't let me transfer shows.
I was getting an 855 error. I deduced that even though it looked like the receiver was recognizing it just fine, the limitation of 2 TB was the deal breaker.
However, I went into windows Disk Management and noticed that the Hopper had created 4 partitions on the drive. 1 - 1TB partition, 2 - 500GB partitions and a 4th partition with the remainder of the space on the drive (nearly 2 TB). I right clicked on the large remainder partition and selected delete. This changed the remainder to un-allocated. I plugged it back in and it transferred fine. This was great for me because I just needed 2 TB of space to move my shows from one hopper to another.
I'm posting this in hopes that it will help someone else.
Good day!