Changing WSUS Server Group Policy Settings via script, code or direct registry edits

Hello;

We have a situation where we have a single WSUS 3.0 v3.1.6001.65 server manging updates for approximately 1500 Windows XP SP2 clients. These clients are in a workgroup and the WSUS settings were originally configured via deploying a Ghost Image prepared with sysprep. The image had the local group policies manually set to point to the original server (call it Server1). Deploying in a AD domain environment really isn't an option at this point. 

We now need to point these clients to a new WSUS v3.2.7600.226 server (call it Server2). I need an automated way to point each client to the new server - manually logging into each client and modifying the local group policy via gpedit would be a nightmare.

I have tried downloading and running an app running under an admin account to each client that directly edits the "WUServer" and "WUStatusServer" values in the registry key:

HKEY_LOCAL_MACHIINE\SOFTWARE\Policies\Microsft\Windows\WindowsUpdate

to point to Server2. All other update-related settings will remain the same. I follow these edits with the following command:

wuauclt.exe /resetauthorization /detectnow

I can reboot the machine and the registry server values still point to Server2 and eventually the clients showup on the WSUS console on Server2.

HOWEVER when I log directly into the client and run gpedit.msc it shows as still pointing to Server1. If I force a group policy update via "gpupdate /force" the client eventually shows backup on server1. This seems to tell me that eventually when the local group policy is updated automatically on each client the same effect would occur even if a gpupdate command was never run.

It seems I am missing a step somewhere - any help would be greatly appreciated. I can find no other definitive way to modify these local policy settings via the command line or via an app but I could be missing something.

Mike H.