For buff, it depends on the angle of course. But I like the shoulder when the shot is there. I have used only solids and penetration isn't an issue.

For elephants, shooting - with a solid - just behind the leg bone works well. Easiest shot if you are just behind a broadside angle. A higher shot can spine an elephant too. Solids only.

In sum, break bones when you can and still be sure of penetration to the vitals beyond.

JPK