[NTG-context] \combinepages[]: Change order

Hello, Using \combinepages[some-pdf][nx=3,ny=5], I get: 1 2 3 4 5 6 7 8 9 10 11 12 However, I'd like to get: 1 5 9 2 6 10 3 7 11 4 8 12 How can one achieve this? (I want to create again a poster out of talk.pdf.) Tobias