[NTG-context] PDF TrimBox

Hi, I'm trying to set the PDF TrimBox for every page in the document. \setupinteractionscreen[trimbox={[81.6378 96.9449 513.6378 744.9449]}] This indeed sets the TrimBox for every page, but it ignores my dimensions, and sets them to the page size. \pdfpageattr{/TrimBox [ 81.6378 96.9449 513.6378 744.9449]} Only applies to the first page, and \pdfpagesattr uses an inheritance that Acrobat doesn't understand (is it allowed?). How can I specify the TrimBox on every page? thanks, Thomas