[xsl] flexibly sized region after

["Trevor Nicholls" <trevor@xxxxxxxxxxxxxxxxxx>]

I have an xsl-fo stylesheet which successfully uses different page-masters
to produce a document with cover sheet, contents, chapters and index, with
headers and footers on appropriate pages. Now I have a requirement which
needs to introduce an additional level of sophistication and I'm not sure
how to do it.

One page master is currently defined as

	<fo:simple-page-master master-name="Std-page"
xsl:use-attribute-sets="page.dim">
		<fo:region-body xsl:use-attribute-sets="page.body" />
		<fo:region-before extent="1cm" />
		<fo:region-after extent="1cm" />
	</fo:simple-page-master>

and it is used with an <fo:static-content flow-name="xsl-region-before"> to
format a header, a complementary <fo:static-content
flow-name="xsl-region-after"> to format a footer, and an <fo:flow
flow-name="xsl-region-body"> to display the main page content.

I would like to create a variation of this format in which the footer is of
unknown size, but its content, while formatted top down, is aligned bottom
up. I'm sure this is trivial but I can't seem to find the magic that will do
it. The page will have content aligned top and bottom, with a variably-sized
gap in the middle. I suppose this is the kind of placement which footnotes
at the end of a chapter would have - but these are not footnotes.

Can somebody point me in the right direction (sorry, no pun intended)
please?

Cheers
Trevor