I`ve read all the topics and i should say that the best way to allow a good hamstring stretch, without stretching the nervous tissue, is to keep the knee in full extension, the ankle in plantar flexion and the pelvis in anteroversion. And to prevent any doubt the neck is arched backward.
One study, made in UFMG, a brazilian university, performed the hamstring stretch in two different way: the first one was the straight leg raising with the ankle in dorsiflexion and the second was the straight leg raising with the ankle in plantar flexion. All the subjects in the groups got their flexibility increased in the same quantity, and no differences were find between the ways of stretch to increase the ROM.

Luiz Fernando.