font size for section titles

How do I change the font size for all the titles with respect to their 
current sizes. For examples, I need all the titles half their original 
sizes. I have check this page 
http://www.sagehill.net/docbookxsl/TitleFontSizes.html and the 
properties reference but could not find what I am looking for.
This example from the page is great:

<xsl:attribute-set name="section.title.level2.properties">
  <xsl:attribute name="font-size">
    <xsl:value-of select="$body.font.master * 1.728"/>
    <xsl:text>pt</xsl:text>
  </xsl:attribute>
</xsl:attribute-set>


but  I need it for all the titles so change the to:

<xsl:attribute-set name="/|section.title.properties|/">
  <xsl:attribute name="font-size">
    <xsl:value-of select="$body.font.master * 1.728"/>
    <xsl:text>pt</xsl:text>
  </xsl:attribute>
</xsl:attribute-set>


but the size here is fixed for all the sections levels.