Thanks, FYI i spotted a mistake on my numbers, no load current should have been 10ma not 0.01ma! sorry, although this is read from my cheapo bench psu so is probably not too accurate.
thanks for sharing the resistor values, i could do with checking what these should be to make the Nexus 7 think it's connected to it's AC adapter. i was going to set this up when i got around to installing into the car, i have to chop off the molded usb socket and refit it to the one thats built into the car dashboard already.