And concerning yin and yang surfaces.... when she would try to push me or pull me there was a very clear distinction between the yin and yang surfaces, and I had to soften to a further degree in order to maintain my structure. As she would push (she would stick both hands on my chest and sort of "charge" into me driving with the legs) the yang tissues would just melt and wrap around the bones on the back side and the yin tissues would kind of dissolve inward and down to the dantien. The softer I got as she pushed the more relaxed and at ease I became the less and less of the force I felt, and as she increased her efforts the relaxation and ease would go deeper, and the yang and yin would expand and condense accordingly. I wish I had the ability to fajin, because I got the feeling that those would be the perfect times to do it. It only took slight movement to either divert her away to the side or push her back, and the mingmen really spread and opened.