Oddly the British Westfalia (Witter) version has the ball head further back than the German Westfalia one. Different designs.
Years ago I contacted Westfalia if an alternative detachable part could be used or recommended to solve the tailgate clearance issue. response was that VW provide very specific measurements as to towbar mounting points and distance away from those that the ball must be positioned. For that reason they couldn't answer my question.
I acquired a second hand Audi one that raised the ball head position but was the same rearward position. Good for lowered suspension. I also have a Golf one which is virtually identical to the Transporter based one, saves me fishing out the one in the box.
You may 'luck' upon one to suit from another vehicle as the plug in end is the same, there are two versions early and late so check carefully what yours is..
A breakers yard may be a source.