With all due respect, I think maybe you are experiencing troubles because you have not perfected your wrap and hanging technique. Skin stretch while hanging straight down may have masked this.
Why do I say this? Because I had the EXACT same problem when I started hanging SO.
See if these old threads of mine help. If not, I`ll try to help out. In essence, I found that I had to make sure the hanger was gripping the structures and "settling" while using a light tug as I tightened. When I felt it was grasping the structures, I tightened it all the way down.
In the past, I would attach the hanger and immediately start tightening the hanger, but when I attached the hanger it would always slide toward the head no matter how tight it was because I had not done what I mentioned above first.
How I attach the hanger!
Anyone successful with hanging straight out?