Thank you for your replies. I will certainly try that bubbling wellpoint though i do not think i know 100% what you mean?
According to my understanding, whenever there is external there is always, always internal. Whenever we speak of internal, there is always, always external. To simplify things, teachers may speak only of one or the other, but the other is always, always implied. Students may understand or relate to one or the other, but the other must always be understood as well. If you truly understand one, you will understand the other; but often you cannot be sure you understand one, without analyzing the other. Depending on the teaching or learning style and depending on the teaching or learning moment, one principle will be better to consider than another.
The above quote relates to internal things, by naming an external point on the foot where the energy needs to be rooted. As I understand and feel it, this point is right behind the pad of the ball of the foot. It is the point you would thrust against, if you were to jump straight up and draw energy both from the ball and the heel of the foot.
To avoid developing and to help treat knee problems, it is good to look at the desired external structure in the legs. The crotch should be rounded, kind of matching what happens with rounding the back. The knees of both the front and
the back foot should be bending in the direction of the toes, the front knee pointing forward and the back knee bending at a 45 degree angle. It is quite dangerous for the knees to bend repeatedly inward with respect to the direction of the toes. The joint is not designed that way. You do not want to increase very much at all the lateral flexibility of the tendons that hold the knee joint together. It also a little bit dangerous when you are in a forward weighted bow stance to have the knee past the front toes, since this also stretches the knee ligaments unnaturally. Back-weighted stances and empty stances are different.
From a more internal perspective, you can think of each knee as being the middle of a bow that is made up of the foreleg and the thigh. For the energy to flow correctly, the bow must be bend forward and backward, but not side to side. Bows are constructed and trained to bend in only one way. If you bend one in another way, you can destroy its power permanently. Even when you bend a bow properly, it will emit power in only one very specific direction, from the middle of the string to the middle of the bow. If you lay the arrow so that it intersects the bow and string at a different place, the result will not be good. Similarly, when you have the weight forward in a bow stance and allow the front knee to pass the toes, your front leg will have too much and your back leg too little.
I personally think in patterns and look for some kind of "handle" or unifying principle that can stand for the entire pattern. What I do to accomplish all the above is to feel for the energy going through the bubbling well point. If I stand naturally with my feet shoulder width apart and my intent is to stand for awhile, I feel that my legs stand in a "V." The pressure is on the inside edge of the soles. My weight is usually somewhat towards the heel. My knees and crotch close to take pressure off my muscles. This is great if my purpose is to stand for awhile with minimal expenditure of energy, which is a very specialized goal. This is bad if my purpose is to stand for Tai Chi purposes, which require a much more neutral equilibrium. To achieve my Tai Chi goals, I feel for the bubbling well point. To feel my energy come from this point, I feel I have to even out the left-right pressure in the sole of the foot. To do this, my knees have to move apart so that they are more over this point. To do this, I have to open the crotch. The feel of my legs change from a "V" shape to an inverted "U," which feels much more stable and powerful. To increase the clarity of the feel of energy, I must also bend my knees a little and rock my weight a little away from my heels toward the ball of the foot.
You can do the same process in a bow stance, with a similar result. You should feel a spring in both legs. If you pick up the heels slightly and bounce or even jump up an inch or two, you will jump up straight and feel very stable the entire time. If you jump with the knees out of alignment, your jump will tend to pull your feet in the direction of that misalignment and you will feel some instability as the legs push in different directions.