The Specify Full Path option used with File Copy only works for copying files to the startup volume. If you try to copy to another volume, you see this message:
"Can not replace on 1 of 1 computers. Didn't copy '<filename>'. 1 of 1 items not copied."
When you want to into the path:
/Volumes/Non_Startup_Volume/ ...
Drop the "/Volumes/" and enter the path as:
Non_Startup_Volume/ ...