I don't use BSL as a milestone either, I use BSB, because it never changes. BSL depends on whether you're using the top bra strap or the bottom bra strap, and whether or not your bra is properly fitted. People forget that most women's bras do not fit properly, and may sit higher or lower than they should. BSB to waist on me is 5 7/16 inches, and I'm 5'2". BUT if I measured from the bottom of my bra strap it would definitely be less. The length of someone's torso does not necessarily correlate with their height. You can be short with a long torso or tall with a short torso, so shorter people do not always have an advantage when it comes to growing hair. Not to mention growth and retention rates. Reaching hair growth milestones really is unique for each person.