Promises & Servers

Hi everybody, first post here, just lurked for a while...great site. I'd like to ask you experts something, so... I have a customer (an adv agency) with 10 Mac OS X clients (mixed versions from Jaguar to Tiger) and an old Xserve G4 with Tiger Server installed (standalone config upgraded from 10.2 NetInfo :-((). Unfortunately I inherited this situation, which drives me crazy. The former consultant, who has never had a proper sever training of any kind :-(( (again here - read: no experience at all in a server enviroment) promised the big boss that each client will have 20 GB space on a "reserved folder" for backup purposes. Now...through all my searches I've only found out you can just have disk quota control for what concerns network home folders. Just my luck! ;-) Is this true and correct? Are there any methods to implement this kind of stuff? Any workaround? Is it possible to use fixed-size .dmg to be configured as users shares? Thanks in advance for your help/suggestions. Cheers, David