Hello Phil,
As part of our implementation, long name support is rarely used but must be tested by most of our products. In some test Endevor instances, I've created USS Base libraries and use a PDSE for the Delta. I also used REVERSE setting in the Type definition.
Since the path of the BaseLib cannot be defined, I use the ESYMBOLS table and define a symbolic for EACH stage so I can know exactly where the directory structure is located.
The File System is unique for the Endevor instance so I make sure that the VSAM file is mounted after every IPL and the mount point is a ROOT using the symbolic structure as defined by the ESYMBOLS table.
I make sure that the permissions for the file system directories are set to 777 so that there isn't any impact through access, but I understand others may want to restrict that and provide the Endevor Altid with permission to access the directories (not sure how, but there it is).
There is really no trick to this EXCEPT you need a File System large enough to handle the amount of elements to be stored within.
Bernie