Christophe, and others, my sincere apologies if my first comments were taken as being whatsoever derogatory, that most certainly was not intended.

I always try and solve a problem with a simple solution and one that is easy to implement. In this case I could see an easier, simpler and quicker solution, that's the only reason I mentioned it. I suggest the majority of followers of this site do not use CAD CAM software or have access to a 3D printer and err towards a simple approach.

Christophe, you have produced a very creative and elegant solution which doesn't require modification to your shredder although if I may say, a somewhat complex one. Congratulations on your win.