Can I constrain brush softness to the actual size of the brush?

Right now, when you choose a brush hardness of 0 (maximum softness), the feathering extends beyond the brush's displayed radius. I need to be able to constrain it so that it is fully contained within the size I have set for the brush.

As you can see in the attached video, as I paint with a hardness of 0, the paint exceeds the brush border by at least 50%. I'd like to constrain it to the size of the brush, so that all of the feathering lives inside the brush's border.