I have a PT that showed me a great way to stretch. I too had (have) flexibility issues on the hammies. He has me lye on my back, puts my ankle or calf on top of his shoulder and has me push down as hard as I can. After about 10 seconds of me pushing, he has me relax. At the same time I'm relaxing he'll stretch my hams. In a matter of a few reps of this, I'm almost touching my knee to my nose w/ no discomfort at all.