Tag Historian - Moving tags between gateways

I have a gateway which has been a combined frontend/backend gateway, which has several other backend gateways connected to it.

It has been decided that this should now become a dedicated frontend server, and we want to move the connected devices and tags to a new backend server, and delete all tags on the existing gateway.

Most of the tag history is not critical to move over, but the customer has a few tags (30 or so) that he would like to be accessible on the new server.

We would like the old tag history to be combined with the new.
What would be the best way to do this, without messing up the taghistorian database?
Can I just do a sql query to edit the "tagid" field from the old data partitions to match the tagid for the new backends tag?