To allow things like battery compartments I added a new lid type consisting of 6 new edge types. Well, more like 2.4 new edge types. Two are FingerJoint- and FingerHole-Edge with a new "play" parameter and two are the left hand sides of the actually new ones. An edge with "pins" that lock into slits of the opposing side walls.
The new lid can already be selected in the Box2 generator.
Next step is adding some (optional) springs in the lid to keep it in place ven without batteries pressing against it from inside.