How to modify/update the Master Image

Hi,

I've vWorkspace 7.2 MR1 over VCenter 4.1.

I've a Windows 7 Master Image Base with 3 snapshots. The first one (SnapShotBase) is the snapshot of the Master (this is like a root snapshot) and then I've two more from here: SnapShotOpenoffice (for desktops with Base + Openoffice) and SnapShotMSOffice (for desktops with Base + MS Office).

There are 2 computers groups: one running from SnapShotOpenoffice and another from SnapShotMSOffice.

It seems that modify parent snapshots will corrupt all dependents VM!, so, how can I update all the Windows 7? It's possible update only the SnapshotBase and "propagate" the updates to all the dependent snapshots and VM or have I to update all of them independently?

What are the best practices to do it?

Thanks.