I have finally got around to posting the iliacus release that will help to open the hips. The psoas and iliacus are different muscles and need to be mobilised differently. A tight iliacus will cause the hip to flex which makes hip extension past 0 degrees almost impossible. As it flexes the hip it will anteriorly rotate the pelvis. Alot of of GST needs a good PPT so a tight iliacus is our nemesis.
These are a release so you need to spend a long time in these positions to get the benefit. I will at times watch TV in these positions for 30 minutes. They should be used to compliment the more aggresive stretches done in the Front Split series and the active mobility that is done in Foundation and Handstand.
I rotate through each position every couple of minutes. The idea is to get the pelvis to PPT effortlessly and let the front of the hip open. Do not force these positions as you are trying to relax so the brain thinks their is no threat and will ot spasm the muscle to fight you.
The iliacus release works well in conjuction with the psoas release. So if you have one hour of TV watching get off the couch and stop shortening the anterior hip.