i see that it could be a problem if you did it too much, but essentially all you're doing is preloading it a little. It's basically the same thing as using a coil spring on a strut that's longer than the strut shaft (like most factory struts do). Correct me if i'm wrong? I'm no expert, especially on VW front ends
The reason i say this, is because i think this is what has been done to the car i own by the previous owner, cuz the front end is very stiff and i assume they didn't replace the torsion leaves.
Nick