Like Bock E said in the previous comment, where you're looking matters. I do spot the rail because I have to see that I'm going
to hit it, then shift my gaze towards the end of the rail or beyond. It is times when I catch myself looking down at my feet or somewhere else, that I fall off the rail too early.
You can kind of see what I mean here, although this video doesn't really have the best perspective and also it is a 180 on, but I would take basically the same approach to a front 50/50 on that rail.
I slip out a little early but this is because I'm still dialing in that 180. Watch it again though and you'll see that I don't really lock on to the rail until about 0:17, I'm definitely going a few feet down the rail before I'm actually on top of it and that's what I'm talking about.
This is a relatively short rail, but you can see how if you land a few feet further down the rail you're going more forward and less "up" when you pop off the lip. That should help you if you are suffering from white boy can't jump syndrome