WIP - Walking Technic Biped Prototype (balancing problem)

I’m working on a Technic biped and this is the current stage of the design. The main challenge is keeping the center of mass inside the support area during the step cycle. I’m using a side‑to‑side shifting mass to balance it, but the amount of weight required to stabilize the system becomes too high to be practical. I’ve already built a working quadruped, so I’m familiar with walking mechanisms, but a biped is a completely different challenge. Here’s the rendering of the prototype. Any...