In my own, personal and professional experience, I have found that when the psoas muscle is tight, direct palpation and manipulation of it will help it to relax, an assist in creating length. Have you tried finding a massage therapist who is willing to perform this type of service? Typically, for best results, a therapist may choose to follow up with some PNF stretching. If you choose to try this, I would interview your therapists carefully, and make it very clear that you are seeking this specific service.