I saw this somewhere a long time ago. Take a 1/2" PVC pipe and cut it to 10.5". Now cut that length wise just about in 1/2.

I've used this for awhile. All my RX-7's have one. You only need one per vehicle. Easily stores under the hatch carpet.



Here are more pics.

 

i just put a slight bend in mine. but good idea non the less.