Charles Bevan wrote:
The grass shows a sense of formality and rigidity, but the pot has informal look with smooth, free-flowing curves. I believe that a masculine pot with defined lines would be much more fitting for this display.
I think mixing the informal with formal is the whole point. The free-flowing curves are the counter-balance to the straight vertical lines. The Ying balancing the Yang, remember? The whole crux of Asian philosophy.
Based on your recommendation, Yin requires more Yin. What are you gonna do with the Yang?
Using straight-lined pots for straight-line vertical grass would lead to a rigid, sterile display. Everything would be made of straight lines, rather boring if you ask me. What you are saying is a knee-jerk reaction to the rule "masculine tree asks for masculine pot". There is also another rule that seems to require the opposite, and I remember Robert Steven mentioning it in one of his displays: the masculine character must be softened by feminine character within the same tree, in order to obtain the perfect mix. Mind you, the two character should never cancel out each other, so the portions cannot be equal
Think about the picture of a marsh or swamp where out of the water rise the straight stems of the reeds and grasses. The water is informal, soft, lots of shades and shapes underneath. The reeds and grasses are straight and nearly vertical. The two complement each other perfectly.
You should always think in terms of opposites, when trying to achieve an artistic effect. Whatever the subject, opposing characters will always have a much more natural and therefore more powerful effect.