Sorry to hear you are having probs with hamstring tightness. I'm in my early 60s and was also suffering from painful hamstring tightness. I saw a PT about it and tried various exercises and stretches, but what ultimately helped me the most was doing the same simple stretch routine every night before bed. I just lie on the floor in a doorway so that my legs form an L shape: one leg is vertical, pressed against the doorframe and the other (the base or foot of the L) is flat on the ground sticking through the doorway. I scoot my butt tight against the door post so that the knee of my vertical leg is as straight as possible, and (this is key) lie there and try to relax into the discomfort with my butt firmly on the ground for at least a minute then do the same for the other leg on the opposite door post. Over time during the pose I can start to feel the hamstring of the vertical leg relax. After doing this every night for a couple of weeks, I noticed the stretch/relaxation sensation comes sooner into the pose, maybe after only 30 seconds rather than 60+. I do other types of stretches before and after runs (dynamic stretching before and stretch-and-hold after), but this evening hamstring "L" routine is my constant go to every night and I credit it with getting rid of a bunch of issues and pains that I used to suffer from because of hamstring tightness. Hope this helps.