fat chapter titles

I use xsltproc and the fo docbook.xsl from Norman to generate fo, which is
further processed for print by fop.
I append some modifications to the stylesheet defs, e.g.:

<xsl:attribute-set name="section.title.level1.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>

This works for the section titles (1.2* smaller than the default which is
2.0736* master size).

I can not find a similar attribute for chapter titles.  How do I customize
that?

	Thanx,
--
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	Tom "thriving on chaos" Peters