The harness/jnlp.xml hardcodes many things, which makes it hard to configure and at least in one case is a defect:

1) <j2se version="1.5+"/>
 - This might not be correct. It should respect the Java Platform selected for the project (nbjdk.active, nbjdk.home,
etc.) -> DEFECT
 - It should allow to set the other attributes via properties (java-vm-args, initial-heap-size, max-heap-size, href,...)
(See also http://www.netbeans.org/issues/show_bug.cgi?id=64618)

2) <property name="netbeans.user" value="$${user.home}/.nbapp-${app.name}"/>
Allow to specify the user-dir (.nbapp-${app.name}) and user-dir location ($${user.home}) via properties.
The clean target has to respect this.

3) As the master.jnlp file, the web.xml should be created, if it does not exist, but not to a tmp directory but rather
to "Important Files", where one can adapt it.