11 years old, he is right at 5' 2.75" tall and weighs 150 lbs. he is stocky. he's very athletic in 3 sports. what do you think his adult height will b?

The most usual: height predictor is done by pediatricians when the baby is 2: double his height at age 2! Other estimators use a calculator taking into account the parent's heights: add the mother's and father's height together, add 5 inches, divide by 2. This is purported to reliably give a result within 4 inches of what will really happen. That's about the best GUESS I can give you. Good wishes:)