Can I attach multiple ConfigurableJoints to one RigidBody (closed loop of ConfigurableJoints)

I'm trying to suspend a box from 4 chains, like this, but in 3D:

The chains are made of ConfigurableJoints. When I attach the last link of the chain to the box rigid body, to the last link of the chain, it dangles like you would expect. When I attach the second chain, the physics goes nuts, throwing the box far aways and the chain links of both chains flying wildly around the scene. This is true whether I use ConfigurableJoint or FixedJoint to attach the box rigid body to the chains.

Both chains are suspended to the same Rigidbody at the top, as well.

Can Unity physics handle closed loops like this?