hamstrings are only side of the joint. hip flexors, adductors and ankle flexibility make a bigger difference for me WRT to depth.
I also don't believe in tight hamstrings as much as I believe in weak hamstrings. I tried for years to get my hamstrings to loosen up and quite pullign on my low back, was really bad when I was mMTB racing, woudl just seize up after 3-4 hours. tried all manner of stretching, RDL's fixed it in about a month.