I am using FOG as a base-image-deployer library for VMs, seldom registering a machine on FOG
Ok so you are using fog in a system builder mode. Where you just pxe boot and then select deploy image from the FOG iPXE menu (i.e. load and go). In this case the location plugin will not help you.
Are the master node and storage node at the same location or different geographic locations? If they are different locations and you are using the load and go method, you may be better served by installing a full fog server at each location, then on the HQ location add the two remote FOG servers as storage nodes. This way the images will replicate from the master HQ fog server to the remote FOG servers. The only thing you will need to do is export the image definition from the master node and then import it into the remote fog servers.