It has been my practice to teach and perform this technique with the fists slightly wider than the elbows and slightly higher than the elbows. Volume 3 photos shows fists slightly higher than elbows (Slight incline of forearm) but forearms are parallel - fists as wide as elbows - not wider. Volume 9 additional techniques for Chun Gun specifies "The back fist comes to the same level as the elbow joint" and photo shows forearms level with the floor. Also parallel. What is your practice?