Heinz and others.
Important that when the car is jacked up that the reduced height of the rebound rubbers does not allow the ends of the U bolts to touch the chassis. If you look back through the photos you will see that the thread exposed on Heinz's U bolts is shorter on the side near the chassis (I am sure Heinz has checked this).
Regarding the apparently shorter dampers when on full compression: it may be that these dampers have an internal conical rubber bump stop. I don't know about the AVO but many dampers of this type include internal bump stops.