Greetings!

It should be fairly harmless. Fortunately, I intend to do the copies in parallel. Twice the throughput - I will be copying files on both empegs at the same time...

1) Start configuration: Source [ s0 & s1 ], Target [ t0 & t1 ]
2) Swap: Source [ s0 & t1 ], Target [ t0 & s1 ]
3) Copy: Source [ cp /drive0/fids/* /drive1/fids ], Target [ cp /drive1/fids/* /drive0/fids ]
4) Copy stray files: Source [ cp /drive0/var/* /drive1/var; my archive directories and symlinks, etc... ]
5) Swap: Source [ s0 & s1 ], Target [ t0 (s1 copy) & t1 (s0 copy) ]
6) Adjust Target Jumper / Position: Target [ t1 (s0 copy) & t0 (s1 copy) ]
7) Close up, resync and test