Cisco AAA/Identity/Nac :: ACS 5.2 - Adding Custom Attributes For Juniper Netscreen TACACS+?

I am trying add custom attributes for Juniper Netscreen TACACS+ authentication to a v5.2 ACS. The advice is to add it to the group as follows:
 
ervice = netscreen {
vsys = root
privilege = read-write
} I know how to add this to a version v4.x ACS

However, I do not know how to apply this to the custom attribiutes to a v5.x ACS?do I add the vsys and privilege attribute seperately or together? What should be the attribute name? netscreen? Should it be mandatory?