I used to have one years ago on my Spitfire, I always put the upright at the rear - seemed a natural place for it to help stay the luggage.
Googling images and it seems that the rack is fitted either way in equal measure so maybe its just down to the user and how he sees fit to put it on.
I can see the point in putting the rack the other way up, to protect the rear plastic screen from flying luggage in the event of hard braking or, god forbid, an accident. But it still shouts out to fit the way Graham has, to help support the luggage.
My vote is to put it the same way Graham has, any other wisdom on this one, lets see how many would fit like Graham and how many as Andy would! So far Graham 1 Andy 0
Sundance