XMLBeans and Substitutiongroup

Question

I'm trying to generate an xml document (an SLD file, to be precise) using XMLBeans.

Ideally, I want an output like:

<PolygonSymbolizer>
 ... stuff
</PolygonSymbolizer>

However, what is being outputted is:

<Symbolizer type="PolygonSymbolizerType">
   ... stuff
</Symbolizer>

Even when I try to do an XMLObject.substitute, it doesn't seem to be taking, as my casting afterwards throwing an exception:

SymbolizerType st = SymbolizerType.Factory.newInstance();
PolygonSymbolizerType polySymbol = (PolygonSymbolizerType) st.substitute(new QName("http://www.opengis.net/se", "PolygonSymbolizer"), PolygonSymbolizerType.type);

Any ideas on how I can get it to use the sub-element instead of the super-element?