I've noticed that the balls that eat the best have the smallest heads. I believe this is true because their bodies grow faster than their heads. (soft tissue tends to grow at a faster rate than skeletal tissue--and the head has much thicker bone tissue than the body does). Thus, the ones that eat every time will grow their bodies faster than their heads so their heads look small in comparison to their bodies. As they get older, and their body growth slows down, their heads grow at a faster rate than their bodies and they look more "balanced".
Interestingly, my favorite albino male eats like a pig and has a small head--- and another albino male I have that is a problem eater, has the largest head proportionally of all my ball pythons.
Rodney