Another idea inspired by the Rock N Road 4x4 nets - they offer these overhead cargo nets for Land Cruisers:
The Land Cruiser doesn't have roll bars, so that net has to screw into the headliner but here's an idea for a Jeep - make the net out of the Home Depot ratchet straps I mentioned in the last post and secure it across the roll bars using the hooks on the ends of the ratchet straps and tighten it with the ratchets.
Since the Home Depot ratchet straps are 15' long and the roll bars on a Jeep are less than 5' apart, the straps can be cut to provide the crosswise ratchet straps and there will be plenty left over to make the longitudinal straps. Staple/sew/remove staples like I suggested in the last post.
The ends of the ratchet cross-straps will wrap around the roll bars, and the ratchets will tighten the net so it supports the load very firmly and doesn't sag much. It would look something like this:
I sized the one in the drawing above for the LJ - I measured the roll bars in the LJ and a net that's roughly 4 1/2' wide x 30" long will cover the usable area above the horizontal part of the rear bars. Spacing the straps on a 6" grid would require 6 straps as shown above, so 6 x $1.75 = $10.50.
If you could use an overhead net, a high-quality, ratchet-tightened one for ten bucks seems like a great deal. I think the use of ratchets would make an overhead net much more rigid than a net with some other type of adjuster. Maybe I'll make one up to see how it works out - if I decide to make one I'll post step-by-step instructions.