In nymphing, it's often recommended that you add two or three small shot each spaced an inch or so apart on your leader rather one large shot. That's what I do.

But, I'm not sure I understand why -- unless the reason is that it's easier to fine tune how much weight you're using. And why space them rather than bunch them up?

Fortunately or unfortunately, I'm the type that has to understand why, and I would appreciate some help on this one.

If you have an answer -- thanks!