Just remember if using GP to place computers in group you have to tell WSUS server that this is the case;
Options –> Computers –> “Use Group Policy or Registry settings on computers”
On replica servers ensure that the status is rolled up to the upstream server;
Options –> Reporting Rollup
Ensure that the Upstream server can see the status of all PC’s
Options –> Personalization –> “Include computers and status from replica downstream servers”