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[email protected] I don't find a translation to "concertable" in my language (French) so I'm not clear about your first phrase.
Also my idea is not to grow the objects but rather shrink (and shake) the box. To be more precise the box would be thin in depth to make sure the objects don't fall behind each other and the extrusion would be thin enough to ensure the smallest objects don't rotate in an undesired direction.
Of course a 2D physics simulation would be much more optimal. Maybe there's an app for it?