Try the Yoga head to knee sitting forward bend 'Janu sirsasana' with your Flexistretcher to assist or to intensify the stretch.
Here is a great step by step how-to: http://www.yogajournal.com/poses/476
Practicing this stretch with your Flexistretcher brings a whole new level of awareness allowing you to sink deeper into the stretch no matter what flexibility level you are. Remember to activate the muscles of the out-stretched leg by pressing into the strap and pull the loops towards you as you fold forward.
Cues: keep hips square
Modifications: Bring the foot of the bent leg to the calf or ankle of the out-stretched leg to decrease the stretch.