Apparently adding a rear lightbar is a popular add-on for Ventures. John said they even sell a $50 kit with brackets. John bought just the light from KMT Parts and we installed it when we installed his front lightbar.
For awhile we pondered making an 'L' or 'U' bracket similar to what he had seen on the web. Nothing we thought of really appealed to us. I noticed the holes in the lightbar almost lined up with the holes in the trunk rails. We found some 1 1/4" brass spacers I had and some long 5mm bolts, and put it together.
It worked great! The lightbar sets right behind the rear trunk rail and is rock solid. We ran the wiring under the trunk to his taillight and covered it with ziploom. The best part is it didn't require drilling any holes. John modified the rubber trunk rail covers for a custom fit.
The rear lightbar works great. The running light part accents the stock taillight and the brakelight part is very noticeable. Being higher it will help when he is pulling his trailer.