[NTG-context] Footnote in columns interlinespace

[Michal Kvasnicka]

Good noon.

I typeset a document in two columns on the grid. Footnotes I place in
the "columns".
    \setupfootnotes
      [rule=off, way=bypage, location=columns, conversion=set 3,
before={\blank[line]}]
    \setupfootnotedefinition
      [location=left,width=fit, sample={\mathematics{\star\star\star}\
},hang=1]
How can I set interlinespace to a smaller distance? (I don't care that
the footnote lines would not be on the grid---I prefer it to a very
loose interlinespace.) I guess that there is better way than to write
    \footnote{\setupinterlinespace[line=9pt] ...\par}
Moreover, it doesn't work well since on the first line is apparently
inserted a strut.

Many thank for you help.
Michal Kvasnicka