Théun, as a martial artist I would like your perspective on the placement of weight. I ask because within the martial arts there are two schools of thought on this one. The one school maintains that it is not important, whilst the other teaches it as being of great importance.
I don't know much about the martial arts, so in order to answer your question I will draw upon my knowledge of both DANCE and GYMNASTICS.
The PLACEMENT of WEIGHT is crucial to not only MOVEMENT, but also to the PREVENTION of INJURY. If the body weight is incorrectly aligned and placed movement is seriously impaired, and BECAUSE the movement is impaired injury is more often than not the result. In other words, once MOVEMENT is INITIATED it has the POTENTIAL to make you FLY or to CRIPPLE you; the DECIDING factor is WEIGHT PLACEMENT. :)
Both dancers and gymnasts are put through hours upon hours of gruelling training in order to LEARN how to align and place their body weight. Once placement of weight has become a CONDITIONED REFLEX, the artists are taught to INITIATE the MOVEMENT, and then to ABANDON themselves to it by RELAXING FULLY into what follows. The result? Because weight placement has become a conditioned reflex, the body USES the MOMENTUM of the movement to AUTOMATICALLY CORRECT itself even IF, for some reason or other, the LAUNCH was slightly off-balance! This, within the arena of MOVEMENT, is what is termed DYNAMIC STABILITY. :)
Needless to say, this second part of the training is FAR MORE difficult to master than even the first part. Why? Because whenever the body is even just slightly off-balance the MIND panics, kicks in and WANTS to correct the weight, with the result that the body TENSES, the tensing AUGMENTS the lack of balance and the result is......SPLAT! LOL!
Now apply what I have said here to MOVEMENT, that is, ACTION as understood within the teachings. And realise that the moral of the story is that although the MIND can be very dynamic, it is not very good at achieving stability, other than, of course, the INERTIA which comes AFTER a FALL! LOL!