Storage unit permissions question

Hi,

We have netbackup 7.5 with mixed Windows and Unix servers and Data Domain storage. 

When a backup occurs the primary copy is written to one Data Domain box, then a duplicate is sent to the second remote Data Domain box. We have one main storage unit for each site. At the moment all our media servers are ticked in "Only use these media servers" on both the storage units. 

Should only media servers on site 1 be able to access the storage unit on site 1? And same for the other side: only media servers on site 2 allowed to access the storage on site2? Will duplication still work with this config?

The media servers are enabled with DD boost plugin on both DD boxes. 

Thanks!