My apologies, I should have mentioned the servers are all 10.4.
10.4 OD servers don't have that key, but 10.5 OD servers do.
You don't have to do it that way.
SUS is just Apache.
What I do is have my master server run SUS.
On that same box I have an Apache (the 'real' apache) set to serve the
same location as SUS, with index pages enabled.
Then on other servers (that don't need to even be running OS X....)
you simply use wget or some other recursive HTTP sync tool to
synchronize the directories.
There's nothing stopping you alternatively using rsync or something to
sync the locations as well, but wget is better for my environment due
to other replication strategies that are in place.
So really to have slaves, they don't need to run SUS, they don't even
have to be OS X, they just need to be a web server, serving out the
right kind of content.