Hi Kip,
I don't think you can declaratively do this by modifying the manifest.xsf, but you can use File->Extract Form Files, close the designer, and open manifest.xsf in notepad. Search for the control.
The other obvious thing to do is to add an OnBeforeChange event handler. Add a condition for Delete operations and return False. InfoPath will prevent the user from deleting the row, but they will still get the widgets.
A third way to do this is to hide the widgets and add your own buttons that do the insertion. This way it's cleaner because there is no confusing widget.
Good luck!
Patrick Halstead [InfoPath MVP]
InfoPathDev
Patrick Halstead
Project Manager at Qdabra