DS920+ storage pool expansion - issue

[fropdaddy]

I have a DS920+ running DSM 7.
I am running SHR with 3 drives:
5 TB
14 TB
14 TB

I was able to acquire a 12 TB drive and was going to expand my SHR, however I found out in the fine print that you can only replace or expand a SHR drive set with a drive that is equal or larger than the largest drive in the drive set...
This means that the only way that I can add this drive to the drive set is by remaking the drive set which would clear all the data on the drive set (and possibly all the settings on the NAS).
I would be able to borrow a DAS, connected via USB to the DS920+, that would be large enough to copy everything over so that I could remake the drive set.  Is there a way to do this and be able to keep all of my settings and permissions so that I don't have to reconfigure all of the backup clients, plex logins, etc.?
For clarity, could I back up the NAS via the USB port on the 920 to a DAS (exFAT most likely), remake the SHR with the added drive, then restore all the settings and media?

Or is there an easier way to accomplish this?