I spent many hour researching this & was also on owner of a MkII with a Thule 973. That was great but you cannot attach it to a Mk III in anyway at all. The base of the door is a very wide flimsy piece of plastic not suited to carrying any load at all. My prefered solution was towbar mounted (cos I couldn't possibly reach the roof when I come back from a dirty bike ride across the moors) & I am a convert - hugely stable load carrying even with 4 bikes on a thule 903. Give it a go.