/u/bostonsubboy this is how I did the shoulder. When I brought the rope up her sides I threw a munter knot over that to lock it down.....seemed to help with the sliding off thing.
honestly always LOVED the PRIVATE magazine endings because of the flying cum. Can't tell you how HOT it is to shoot things like this every few days with the love of my life in probably the world's best marriage :) (yes, that's all us)