Because of the good feedback on the volume slider i might aswell give out my hair length slider i have been using myself.
I was planning to make a better one, but its pretty good as is. It can change the pose a bit, but i suspect this is due to the nature of the large amont of area in the image beeing affected with hair length.

Most stable from -5 to 5 but works outside this range as well.
Works very well in combination with my Hair Volume Slider