I hit em on back days, I think it would be too brutal on my leg days to incorporate this one in. Between my leg days and my back days there's at least 2 rest days so recuperation is not a problem. Also hitting the hamstrings twice a week is working well for me.
Was doing them 3 times a week (on back and thigh day so did them for both) up until about 10 weeks ago. I will cycle them back into my routine eventually. I was up to 425 X 6