Re: Training Internal Strength
I sorta feel we're around the limits of what we can have as a dialogue until we get hands on time (or have mutual contacts vet what we're doing) - but I agree with you that there's a joining where the two natural forces of ground/gravity meet. Part of the training is managing the intersection of those forces in you AND conditioning your body to more efficiently manage that intersection (and additional "inputs" - whether they be a weapon, other people, etc.).
If we go back to the "what" . . and describe that as the intersection .. you've used the term "shear" and I think I know what you're going for - but I would add that there's a few other factors you aren't giving due consideration to and may be perceived as a tipoff to others that have extensive time and training in this area.
So there's an intersection and a natural power output - whatever you wanna call it. But at this point there's a conditioned trick for getting that output where you want it to go - hands, foot, head, through somebody else, out the end of a weapon, etc. This involves stretch and elasticity of the body as well around the management and delivery of that intersection - through the bones, ligaments and muscles acting as one unit. I don't go into too much detail online around this, because there's some risks when you haven't been shown how to do it correctly - and I'm a firm believer in this area of the "it has to be felt" principle.
This is where I tend to see the biggest differences in approach, which parts of the body are responsible for the stretch and release, how they're coordinated, trained, etc. The "what" that is moving the intersection is going to depend on your level of training and ability - it could be local muscles, could be the middle, could be the mind firing off micromuscles, could be some combo of things . .