How much easier and gentler it for both client and practitioner to approach the upper psoas laterally; slowly working your way through layers of fascia and going under the rectus abdominus.
Using rocking, deep breathing and active movement by the client allows the tissue to melt, unwind and relax organically without force.
Work as far medial as you are able to safely go to to release the fascial adhesions that often form in this vulnerable area. Softening the fascia and muscle tissue around this portion of the psoas goes a long way. On many people you will not be able actually palpate the psoas and that's ok!