right margin too high

["Johannes Hüsing" <tmi0m0@uni-essen.de>]

Dear ConTeXtuals,

as a beginner I am not supposed to tinker with the internals but I figure 
that's the best way to learn about them...

I chose s-pre-01 as the presentation module. I wanted to include a MetaPost
graphic on the bottom right outside the text area and figured that the 
appropriate position is the right edge. What I included then was 

\setuptexttexts
  [edge]
  [][\vbox{\TopicList\vfill\externalfigure[mprun.1][width=60pt]}]

(according to Hans' hint to use \startMPrun and \stopMPrun to be able to
scale MetaPost graphics).

The \vbox I get exceeds the text body in height and the first topic is 
pushed above the visible area. I find that odd because I thought the glue
would stretch as long as to fill exactly the height.

Does anyone have an idea?

Thanks and greetings 

Johannes