To help improve my visibility, the first thing I did was fold down my center front seat. That helped a ton. While the three rear headrests still block my view a little bit, I can live with it. I still have to lift myself up a bit, but at least now I can look out the window. The next task was figuring out how to line up my truck's ball with the trailer's gooseneck without being able to see it.
All I do is place the rock at the end of my tailgate so that it's directly in line with the ball (see photo above). Once I am in the truck, I look out the window and line the rock up with the gooseneck. I back up slowly, keeping the rock and hitch in a straight line. Now, I never miss.
So that's the story of how a rock made my life a lot easier.