Hi Jim,
Easiest way to do it is to modify the downloadConfig.xml file in %ProgramFiles%\VMware\Infrastructure\Update Manager (assuming you installed it to the default)
You'll want to set the following:
I also mod the patchStore node to specify a different store location, annoyingly this cannot be set with an install switch.
And yes, the documentation is rather scant but then again I guess it doesn't do much, from the looks you could almost install it via xcopy :smileyhappy:
Cheers