[NTG-context] stacking margin notes

I was expecting this to work: \setuplayout[ width=10cm, backspace=10cm, leftmargin=8cm ] \starttext \inleft[stack=yes]{ \input tufte } \input tufte \inleft[stack=yes]{ \input tufte } \stoptext but it doesn't stack. Also, is it correct that stack=yes belongs into \setupmargindata? Thank you, Severin