[Christ]

Wow -

I just noticed that he's got a third brake light on that cap... never saw it until now.

Strange, take a pic of your trucks' side view, then lay a protractor down and measure the angle. I don't feel like figuring it out from the dimensions, but it's probably a little too steep for an unoptimized front end. No more than 14* seems to be the generally agreed upon figure, with 10-12* being the most accepted.

With a curve, opposed to a slope, you can get away with a much steeper exit angle, but the overall angle is still relatively the same. For the sake of clean separation, a "razor edge" is best for the edge of the cap, something that doesn't allow the flow to attempt to round a curve and dip down toward the tailgate, so you can get a few inches past the tailgate with that as well.