[NTG-context] Centering a figure vertically on a page

Hello, the subject line basically covers my problem: I have a large (tikz) figure, and I want to have it by itself on a page, centered both horizontally and vertically. How can I achieve this? I already know that \setuppagenumber[state=stop] is a good idea, and \midaligned{...} gives me horizontal centering; what about vertical? The problem is that the figure is larger than the text area (and this doesn't bother me, it's a game board and it may extend almost to the paper border), so \vfill doesn't work (and \vss doesn't, either). TIA -- Marcin Borkowski http://mbork.pl