Are you familiar with either the Peter Egoscue Method or the Pain-Free Program by Anthony Carey? Both of these books have a stretching exercise where you lie on your back with your calves resting on a footstool so your hips & knees are at 90 - 90 degree angles. Then you just lay there for several minutes allowing the hips to settle to the floor and relaxing tight muscles in the hip, spine & pelvis areas. I've tried this several times & it does seem to feel good. But I wonder if it actually would cause an incorrect pelvic position?