@adrian-a since you are using a qnap device you might consider converting it into a FOG Storage node. You will give up some flexability but in a way you will make the qnap device the storage location for FOG. Here is an overview. https://forums.fogproject.org/topic/10973/add-a-nas-qnap-ts-231-as-a-storage-node-fog-v1-4
Just one limitation, if you use a qnap device as a storage node AND have all of your data on the qnap device, FOG will not replicate these image files to other storage nodes. Only a full FOG server can become a master node in the storage group.