[NTG-context] Splitting a page in given ratios

Dear all, this is probably even easy in plain TeX, but as I have never learned it properly, I am asking anyway: I would like to have a way to split a part of a page into two columns of different width, so something like \startsplitpage[columns=2,spacing=fill] \startcolumn[1][width=.6 \textwidth] \input{tufte} \stopcolumn[1] \startcolumn[2][width=.3 \textwidth] \placefigure[theBeerBottle] \stopcolumn[2] \stopsplitpage so that the individual columns are treated (if possible) as separate pages with all features (like \framed etc) adapted to the page width of the smaller sub-pages. This could replace (for me) the somehow (for me) disfunctional figuretext construct. Is there a way to do this? Thanks, Matthias