Figures protruding into the margin in double-sided document

["Tim Eyre ティム" <mail@nihilist.org.uk>]

I am composing a double-sided document with wide outer margins to
allow space for figures. One type of figure is in-line with the text
and protrudes into the wide margin. This is easy to do on left-hand
pages by saying \setupfloats[location=right] and on right-hand pages
by saying \setupfloats[location=left].

Is there any way to automate this so that inserting a new page does
not mean I have to fix all the figures? I tried using a macro along
the lines of

\ifoff\pageno\\setupfloats[location=right]\else\\setupfloats[location=left]\fi
but the asynchronousness of output routines means that the page number
is usually wrong.

Any help much appreciated.

Tim