Separator line in region-start

Hi all,

I want to have a short separator line in a region-start positioned 
exactly in the middle of the page (top to bottom direction). I have 
tried something like this but to no success:

<fo:page-sequence master-reference="simple">
  <fo:static-content
	flow-name="xsl-region-start">
   <fo:block-container
	display-align="center">
    <fo:block>
     <fo:leader
	leader-pattern="rule"
	leader-length="100%"
	rule-style="solid"
	rule-thickness="1px"/>
    </fo:block>
   </fo:block-container>
  </fo:static-content>
</fo:page-sequence>

Regards Oliver