The idea that "crouching" accounts for the short stature of the Garage Shooter is ridiculous. Here he is in the Jackson photo.
The shooter is not crouching at all. He is leaning some, but not crouching. The one who is crouching is Oswald. And he has his right knee bent, which is lowering him. The shooter is substantially shorter than Oswald, yet Jack Ruby was the same height as Oswald.
Let's look at Beers: again, no crouch. The shooter's torso is upright. His knee is bent in stride, but that's it. But, the trio is also in stride, and Oswald is towering over the shooter. Again: Ruby and Oswald were the same height.
The height wasn't Ruby's. The short legs weren't Ruby's. The girth wasn't Ruby's. The hair wasn't Ruby's. And the cleanly shaven neck certainly wasn't Ruby's. He wasn't Ruby.