[NTG-context] twoside layout

Is it possible to set only the textwidth and the inner margin for a twosided layout? As far as I can see, backspace sets only the _left_ margin of odd _and_ even pages. \definepapersize[new][height=240mm,width=165mm] \setuppapersize[new] \definelayout[odd][ topspace=14pt, header=14pt, headerdistance=22pt, height=20.2cm, backspace=1.9cm, width=12.4cm] \definelayout[even][ topspace=14pt, header=14pt, headerdistance=22pt, height=20.2cm, backspace=2.2cm, width=12.4cm] \setuplayout \starttext \showframe \dorecurse{10} {\input knuth \endgraf \input tufte \endgraf} \showlayout[1,pt,cm] \dorecurse{10} {\input knuth \endgraf \input tufte \endgraf} \stoptext Herbert