When you attach various accessories to the back of the GoPro, such as the battery pak, LCD screen or Wi-Fi, then try to put into either the head or chest harness the camera will not lie flat and sits at about a 30deg angle.
Not really user friendly.
I just purchased the helmet mount and this solves the issue by pushing the camera farther out and permitting a wide variety of adjustments. Only $8
Might be a little clumsy/awkward but sure I can get used to it.