Prepress Support - Crop marks Apache Fop 2.1

Hi,

I see that Prepress Support is now available in Apache Fop 2.1. In 
particular I am interested in adding crop marks.

https://xmlgraphics.apache.org/fop/2.1/extensions.html

Is this implemented in Docbook 5.1? How would I go about adding it in?

I tried using <xsl:param name="crop.marks" select="1"/> with  <xsl:param 
name="fop1.extensions" select="1"></xsl:param> but it didn't work.

Thanks,

Peter