@dave.opc it should work . Add [NoBak] to one disk, transfer it, then remove the [NoBak] on the 2nd , restart the transfer => the first one will only transfer a delta , while the second disk will be transfered as full . If you put [NBak] on the first one for the second transfer, it will be handled as a disk deleted and will remove it on the replica
Note you will have the same issue if ( when ) you'll need to do a full backup later on, for example if there are any replication issue, or if you want to ensure your base copy is not corrupted later on