After sometime doing this exercise, I noticed I was able to reach lower and lower with my hands (hands to the ground now). But I nearly always got some back pain (even doing it with 3kg only).
I watched this vídeo that showed some really nice anatomy for the compression stretch.
From what I understood, until one can bend over 90 degrees from hip only, one shouldn't be bending the spine nor loading it, but stretching from a laid back (straight back to the floor) and using straps.
What's your take on aproaching this exercise when hip mobility is still lacking?