Managed Clients and Time Machine Quota Not Working

I am trying to get Time Machine working for with quota for the client machines. When setting the Time Machine preferences in Workgroup Manager I specify a limit for backup storage. Time Machine preferences are sent to client machine fine, but when the backup starts it will ignore the quota set. Has anyone got this working?

Server: 10.6.4, Clients: 10.6.4

TIA
Anders