Collision Avoidance | Dynamically changing object size in the model


I want to define a product which is of a simple box shape to be held by gripper during operation in Collision Avoidance in order to insure that robot wont hit the fences with picked product. Everything is fine with new RW15 it is possible to activate/deactivate model objects in collision avoidance with digital signals.
On the other hand, the cell is packaging different size boxes, one box size per operation. Only when the current product manufacturing is over the other dimensions can be selected. Is it possible to change collision avoidance simple shape object dimensions from rapid? Or you need to directly change .xml file configuration and then restart the controller? It direct modification is required are there any convenient techniques for that?