How do I make drag and drop shapes line up on collision?

example attached:

If it was a game of checkers, how do I drag and drop a circle over the top of another when they are overlapping each other completely. Ive tried centering the collision box on the bottom circle and making it small, but alas as soon as the top circle hits it it drops off center. If I make the top circles collision box small it makes it hard to "pick" to drag.

What Im trying to get is that the top circle has to be almost perfectly lined up with the bottom circle before it is "dropped"

Is this possible?

Cheers for any help

Not quite what you are asking for but how about ? (in my test I reset the collision for the black circle to cover all of the circle)

Perfect for what I want. Thank you very much.