It's all about your fit. Assuming you're of the masculine persuasion, you may even want to get the horn of the saddle a little up. (I know, it's a little counter-intuitive.) The important thing is that you should be able to sit comfortably on it without sliding forward or backward if you take your hands off the bars. This will be more or less level across the top of the saddle, the rail orientation is unimportant.

Here's one of mine.