What an excellent blog post by Alwyn. This understanding of a balance between mobility and stability is where Mike Robertson has been headed in some of his recent articles too. You might learn more by reading these articles:
Hips Don't Lie: Fixing Your Force Couples
The Mobility-Stability Continuum
Push-Ups, Face Pulls, and Shrugs (with Bill Hartman)
The information you learn might help you decide the direction to need to go to correct your own specific issues.
I agree with JP though, that an even better approach would be to have a good trainer evaluate you.