I think I got it:
I created an empty folder inside \serverlabprofiles for user "lab01 called "lab01.v2." Path = serverlabprofileslab01.v2
I went to the Properties/Profile tab in Active Directory for lab01 and set the path to the profile as serverlabprofileslab01.v2
Then I logged in to a machine where I had previously set up the default profile to be as close as possible to what I wanted it to be, and logged in on that client as lab01. The default profile filled the profile for lab01. I made a few changes, screen saver, preferences, etc. and logged off. When Win2003server found the folder for the Roaming profile empty, it populated it with the profile coming from the client at log off.
Then I logged in as domain admin to SERVER, and went to servermandatorylab.v2, and emptied out all the contents of the folder ("lab" is the user I have as the main login for students in the lab).
Then I logged on with admin credentials to the client, and copied the profile stored on that client for lab01 to \servermandatorylab, with permission to use for everyone.
Then I went back to SERVER, and went to Dmandatorylab.v2, and changed ntuser.dat to ntuser.man. And it worked!
By following the procedure above, I was also able to make changes to the mandatory profile: Log in as lab01 (a client with a Roaming profile) and make appropriate changes to settings. Then log off, and follow instructions above to empty out servermandatorylab, and copy the lab01 profile from that client to the servermandatorylab profile folder, and change ntuser.dat to ntuser.man.
o All shares for the profiles have to allow "full control" to authenticated users: see http://download.microsoft.com/download/3/b/a/3ba6d659-6e39-4cd7-b3a2-9c96482f5353/Managing%20Roaming%20User%20Data%20Deployment%20Guide.doc
o "Show hidden and system files" must be selected on the Win2003 server, in order to see the ntuser.dat file. After changing it to ntuser.man, change the property back to "hide."