customizing space before refsect elements

Hello all,

I'm looking for a way to modify the spacing before refsect1 titles. I
found how to do that for section titles (see below).

Does anybody know how to do that for refsect1 elements (or refsections
in general) ?

Thanks in advance,

Erik Leunissen
==============

<xsl:attribute-set name="section.title.properties">
    <xsl:attribute name="space-before.optimum">1.0em</xsl:attribute>
    <xsl:attribute name="space-before.minimum">0.8em</xsl:attribute>
    <xsl:attribute name="space-before.maximum">1.2em</xsl:attribute>
</xsl:attribute-set>