I still lost stuff that wasn't secured even with a louvered tailgate.  The wind from semis going by or strong crosswinds can blow light weight stuff right out of the bed.
Even with the V I still would put the louvered tailgate down when hitchhing or unhitching.  So on my new truck I didn't even bother getting one.  
On Mythbusters TV show they tested fuel mileage with tailgate down, net type tailgate or tailgate up....tailgate up got the best fuel milaege.   Of course they weren't towing a 5th wheel, which means the test doesn't apply but I thought I would share it for when running empty.