Quote - That's looking pretty good.  There's still a bit of knee-buckling, or at least an abrupt bending of the knee in the middle of the animation.  How is it looking, in terms of feet penetrating the floor?

Raising the hip has not helped the knee bukle, in fact, contrary to our expectations, it seems to have made it worse, though that will be hard for you to see in these small animations.

Quote - Is there anything I can test, with the walk process, right now?

As I feel like I'm walking through trekle in the dark, hoping to bump into something useful. I think you should follow your own intuition as to what to test. However there is something you mightbe able to do, if you feel like it. In your "AP4 walk", if you could mirror the values from the left leg, in frames 16 through 30, over to the right leg in frames 1 through 15. Then I might be able to get a walk without the toes going below the ground, though I would still need to use the injected geometry to achive this. Only if you feel like it. I tried but keep messing it up.

At the moment I can get the left toes to stay above the ground, but not the right toes, the right toes are still a problem in frames 7 through 11.