There are few things that can make a Mama Physical Therapist cringe more than to see her 6'1 ft son walk around all hunched over with rounded shoulders!  Be proud of that height, Eli!  The only thing I said to him to correct his posture from picture 1 to picture 2 is, "Pretend you have a string on the top of your head and it's being pulled to the ceiling."  Then all of a sudden, he's stacked from head to shoulders to hips to feet.