Never lose sight of the essence!
In ST we always strive for BSS (balance, suppleness, shape) and this not only in movement, but already in the standstill. 
So, always keep the center of mass (COM) in a proper position
During my own ST journey, the lessons with my students and my workshops I already was quite aware of the importance of keeping the COM in a proper position. But during my education as a ST evaluator the importance that the human really is aware of and understands this gets even more important to me.
Because of the horizontal imbalance (because of the relatively heavy head and neck, the front legs carry more weight than the hind legs, which results in an unequal weight distribution between front and hind legs) every horse tends more or less pronounced to have his COM more in his shoulders.
When doing ST this gets already obvious in the standstill and even more when we start to ask the horse for forward-down with his head and neck at a standstill. We always teach our students to reposition the front legs in a more upright and parallel position and with this to have the center of mass in a better position. But many students only check if the front legs are parallel and are not so much aware of the fact that the front legs are not only parallel but also upright. Now the essence behind repositioning the front legs in a more upright position is to rebalance the horse’s COM out of the shoulders and with this in a proper position. If the COM is in a proper position, the front legs will automatically be parallel and upright.
In one of my ST workshops in Tennessee last year we had an excellent small case study about this.
Deb brought her lovely mare Kaatje to the workshop. Kaatje is a frisian mare with a very prominent sternum and a natural way of shifting her COM more towards her shoulders.
At the top:
Kaatje in her natural tendency to stand, when we only ask her front legs parallel. You clearly can see her prominent sternum and her front legs more backwards than upright.
At the bottom:
Kaatje after rebalancing her COM in a more balanced standstill. Her prominent sternum is nearly not visible anymore and her front legs are more upright.
Conclusion:
– Always keep the essence of an exercise in mind and the WHY behind your aids and ‘corrections’.
– Rebalance your horse’s COM always when you are training and be very precise and consistent with it, because for now it feels normal (because of their natural neurological pathway of standing) to them to stand with the COM in their shoulders. If we want the horse to feel normal with the COM is in a more balanced position, we have to change this neurological pathway of standing. This takes time and only can be done through repetition.
Enjoy working on the essence and real quality …