[NTG-context] Creating a folded meander book - imposition problem

I would love to create a folded meander book, but as far as I can see, that means creating a new imposition scheme and that's beyond my skill. What I want is a cross between 2*16 and x=4, y=4 (I think). Here's an explanation and a nice graphic of a 16-page (4x4) meander book: http://stamphenge.wordpress.com/minibooks/meander-accordion-folded-book/ A 9-page version (3x3) would also be nice to have, to make slightly bigger pages when printed on A4. Thank you, Mari (Slowly brewing: an article on using ConTeXt and MetaPost in papercrafts.)