Excellent post Rrxtar,
I'm having issues with posture as well, I need to work my Rhomboids? The muscles that hold the back together that keep the shoulder from slouching.
That's why yoga is a good assistance workout, helps realize your imbalances and helps correct them.
On a crazy side note, remember that guy that couldn't walk properly, war vet, etc, got fat, until he took that yoga thing. Eventually muscles balanced out, he can run now and is fit.
Extreme example, but important topic.
Here it is,