[paulj]

the grab handles for the back seats and the rear latch/tether hooks on the ceiling make for four anchor points. You could run some line between them and connect a net of some kind. Some members have done that already to hold all kinds of odd items.

I've experimented with lines between those points, and found that the line has to be quite tight, otherwise they sag with any load, getting the way of back seat passengers or campers.

When camping the back, I rig net pockets between the grab handles and the upper shoulder strap anchors. On the road, I rig those same pockets, along bungees across the middle of the car, to act as a vertical barrier - keeping gear in the back from sliding forward. This is with a 4' platform in place of the rear seats.