I like bondage that can be used for sex. Sometimes sex happens, sometimes not. But keeping the possibility open keeps me interested and excited.
The big things are a bend to the hips and raising the genitals off the ground.
Sex takes time. So the bondage has to be maintainable.
I keep coming back to chain and floor work.
Knees are often the limiting factor. By giving slightly more ability to move the knees I hoped to lengthen the amount of time that was available for sex.