I see many posts about lanyards on lengths of cord - designed so you don't 'lose' the rig, but not to secure the rig. I think the OP is asking about securing it. Any length of line will make a rig flop around if you let go.
I attach a bolt snap to the base of each handle and sling it like a stage bottle - one on a shoulder D-ring and one on hip D-ring. It is important that the bolt snaps are tied very tight to the handles so they themselves don't flop around, they're rigid. Look up the methods of tying bolt snaps onto bottles/lights etc from tech divers to get an idea of how to tie a very rigid connection.
Now I've only done this for scuba - its more challenging for free diving. I'd experiment with dual D-ring placement at different points on your belt. Perhaps to secure the camera on one hip or across the lower back. The D-rings should be rigid to form a tight connection and stop the camera from flopping around.
Placement of the snaps on the housing is important so it sits naturally and doesn't try to rotate itself on the connection. Personally mine works best with the snaps on the bottom of the handles. Experiment.
Cheers,
Chris