I added one to my MGB, and put the rail to the back because I thought it looked better there. I was having trouble keeping everything tight after driving for a while so I talked about it with one of the "old" guys in the local group. He explained that there was a lot more force from braking than from accelerating, (especially with an MGB) and that it would work better if I reversed it, so I did. It was much easier to keep things secured after that. Plus of course there is the whole "headache rack" issue and, while you are more concerned with what is in front, having your own stuff hitting you in the back of the head just adds insult to injury. Or maybe injury to injury.
Sky NA 2007 Midnight Blue
Sky RL 2008 Carbon Flash - Naked