If a page contains multiple \vfills, the space space is distributed equally between them. That means if you want one-third of the available space above some text and two-thirds below it, you can put \vfill above and \vfill\vfill below.
However at the moment our typesetting system (a heavily hacked up version of Pandoc) is hard-coding a single \vfill below the text. (This isn't being generated by a macro which could be altered with \patchcmd – it appears literally in the TeX source.) Is there anything I can do to insert a half \vfill above the text? \vfill is nearly equivalent to \vspace{\fill}, so I hoped I might be able to do \vspace{0.5\fill} (possibly with \includepackage{calc}), but this seems not to work. Is there a way of achieving this?
MWE for illustration:
\documentclass[a4paper]{article}
\begin{document}
Top of page
\vfill % Needs changing to be a 0.5\vfill
% The code from here on cannot be altered
This should be one-third of the way down the page
\vfill\clearpage
\end{document}
(I know I could redefine \vfill to be \vfill\vfill, but I was hoping for a better solution.)
In case it's relevant, I'm using XeLaTeX.
