if its the same size fitting as the original then you probably wont need to measure it, becuase you will have to take the centre console out to fit and when you turn it over you will see that audi has stamped the outline into the plastic where it goes, so all you need to do is cut out the shape stamped.
well thats what ive found when i fitted armrests to mine and a friends car, so guess it will be the same across the range as mine is facelifft and my friends pre facelift.
otherwise i think still have a template that you could have, i made from a car that already had a genuine one fitted that i took out to put in mine, bacuse i dint knwo about the stamped shape at first.