The only thing I would respectfully disagree with in your guide is the 'neutrality' of your head. The head is not in line with the spine during a squat if you are looking up or slightly above you. It actually puts stress on the cervical vertebrae. True 'neutral' is looking at a spot on the floor in front of you. A great cue for this is trying to hold a tennis ball between your chin and your chest as you squat.