The game is nothing but a numbers game. 9s are highly overrated. They usually are accompanied by serious personality issues. Fortunately, I found one without those issues. They do exist, but they are rare.
Chasing after 9's for casual sex is an exercise in futility and dissipation, but most men have to find that out the hard way, through experience. As you already know, once you've found a 9, she becomes common and you want another 9. Therefore it's better for a man psychologically to accept 7.5s and 8s with better character.
9s tend to be toys. I get tired of most of my toys.
By the way, 5'11" is taller than average. It shouldn't be a concern. Very few women are thinking, "Oh, he's too short".
When you accept yourself fully (I know you don't because you're mentioning your hairline and your height), you will become far more attractive to those 8s and 9s. They can sense your lack of self-acceptance a mile away.
That's why I always advise men to Judge, Judge, Judge. YOU are the judge of acceptable looks and character, not her. When a woman senses that you accept yourself and that you are judging her, that's when the magic happens. When a woman senses that you are judging her, it doens't turn her off. Rather, it humbles her and makes her want to impress you.