Flaws in your squat technique will hold you back from progressing. Overhead squats can improve the squatting pattern and should be a regular part of your strength training program.
The overhead squat requires a more upright posture than the back squat and you're forced to execute the squatting pattern precisely, otherwise the bar would drop to the front or back.
Have a look at the video. You can see the high concentration level of the athlete and accurate execution.
Don't you just hate those stubborn body parts that never seem to grow? This "stubbornness" is usually caused by underlying issues, or more accurately, underlying muscles.
Start your biceps work with hammer curls, then a preacher curl variation like the one here. For safety, finish with heavy barbell curls when you're biceps are fully pumped.