An often overlooked aspect of the quality of a woman's bosoms: the angle between her stomach and the bottom of said bosoms. A 90 degree angle is optimal, assuming that the stomach forms a vertical line. In that case, the bottom of the mammaries would lie on a horizontal line. Essentially, having spillage so that the angle of the melons descends below horizontal is equally bad to not reaching the horizontal.
Man, did you see that girl? Her boobs were huge, but the spillover was excessive: her angle of action wasn't very good.
Duuude, check out her rack! It looks like there's a shelf underneath those babies! What an angle of action!