[NTG-context] How do I setup this arrangement?

I want to use \setuparranging, \setuplayout and \setuppapersize to do the following: 1. Page size is somewhere between A5 and A4 (large paperback book) 2. In draft mode: - Output pages are magnified (<1 factor) to a A5 size - Two pages on one A4 landscape - Ordering simple: (0,1),(2,3),(4,5) (2 shrunk-to-A5 pages on one A4 landscape) 3. In final mode - Output pages are centered on an A4 paper with crop marks I have tried to find information, but the orderings of \setuparranging do not include this simple ordering. G