Full and empty, double-weighted

In the various books on taijiquan there are many references to the concepts and practice of full/empty and double-weighted. I had taken them to be the same thing (and much that I read seemed to use the terms interchangeably). Yet, it was not always clear what was meant. I asked Master Jesse, and his explanation was very helpful.
These are two very different ideas in Chinese, and though the English translation sounds like the same there is a mjor difference.

Tai Chi Colorado Springs Boxing Association
Golden Rooster Stance

First full (yang) and empty (yin). This is the relative weight distributed between the feet. For example, if you stand on one leg (in say, Golden Rooster stance) the foot on which you stand is full (100%). If you stand in bow stance, the front foot is about 70% full and the back foot about 30% full. As you "sit back" the rear foot becomes more full and the front foot empty. In "Play the Guitar" is more like back foot 90% and front foot 10%. Much of taiji is the movement from full to empty in slow and graceful movement. The foot that is full does not move, only the empty foot. This is the way of balance.
There are good pics of the basic stances on the Tai Chi Colorado Springs Boxing Association web site.
What then is double weighted? Though it sounds the same in English is refers to something different: the relationship between the right side of the body and the left side. There is a correspondence between the right hand and the left foot, the right knee and left elbow and vice versa. In taiji form, if  the correspondence is between the right hand and right foot, that is said to be double-weighted and unstable. So, for example, in "Part the Wild Horse's Mane" the stance is bow, with, say left foot forward. The left hand has moved in a circle low to high; the right hand has blocked down palm facing down to the right side. Qi moved from the right foot (back) through the hips, to the left arm to the left hand. The forward left foot corresponds to the right hand blocking down. In this way there is a crossing of qi and great stability.
The key is the intention. Qi follows Yi. Energy follows mind. I take this to mean that as the form progresses, the mental intention is for the energy to flow in the spiraling manner.
Since Master Jesses's lesson I have been practicing this and found it very beneficial. I would say it takes practice to another level again.
Stay balanced!