A buddy has a pile of this stuff laying around. It's surgical stainless steel screen that came from Ice Harbor dam. (It was a fish screen) The stuff is next to impossible to cut or drill.

We used large-head pop-rivets (About 7/8" across) to make it part of the rack. Now, anything can be tossed up onto the rack, nothing can fall past the rack's bars to the roof. The floor works fantastic when used with a Thule roof storage bag.

A major side benefit is the SS material reflects the sun, so no heat makes it to the Jeep's roof itself. Open the sunroof to vent mode, and the Jeep stays barely above ambient inside.



The same idea could be applied by using expanded mesh, either steel or aluminum.