I'm not sure that measuring the distance from the mouse is correct here.

![image](https://f.cloud.github.com/assets/21784/1497566/797b5d2e-4811-11e3-8823-5c679af63915.png)

my cursor was at the top of the element so I encountered this situation.  It is less than ideal because I have to take the HTML element almost out of the bottom drop target to put it in the bottom drop target.  Already, almost 50% of the element has passed the bottom of the drop target.