The correct answer to the Shoulder Sit Back Walkover quiz is the skill is Illegal in Level 3. The back walkover transition from a stunt to the performing surface is a downward inversion. The downward inversion starting in a shoulder sit, which is defined as being a prep level stunt, is not allowed in Level 3. In Level 3, “downward inversions are only allowed at waist level…” per Stunts J3.
A shoulder sit being defined as a prep level stunt negates the argument that the base of the shoulder sit having her hands around waist level and under the feet of the top makes the stunt a waist level stunt.
This ruling and explanation are based on the 2016-17 version of the rules dated August 31, 2016.