<<< I am also not sure that I can lay claim to inventing the term "sunken" in this context, but I used itbecause I was taught that Cheng Manching counseled against straightening either the arms or the legs because this caused the qi to rise. Instead, one wanted to keep the qi in the dan tian. To do this, one had to concentrate on "total relaxation" and sinking into the ground. These principles are, of course, not unique to Cheng Manching's T'ai Chi, but the particular emphasis and physical expression do seem distinctive to me.>>>
Audi I think one way to look at this is exactly the way you say it 'Not unique to Cheng's tai chi chuan " But just tai chi chuan principles, There is no straightening of any limbs in tai chi ' as they say find the straight in the curve' two keeping the elbows 'Down ' or heavy elbows is also a t.c.c. principle and practical.
>>> One teacher I studied briefly with and who said he was a "certified" instructor of T.T. Liang's or William Chen's T'ai Chi (I forget which) even instructed me in a somewhat knock-kneed slump-shouldered Preparation Posture in supposed furtherance of the principle of sinking the qi to the dan tian and avoiding extended postures as too tense or as revealing too much.>>>
Well that's just plain and simple 'Wrong ' the Classic say drop your shoulders relaxing the chest allows the chi to settle in the dan-tien and at the same time this idea rounds the back. all this knocked knee and slumped shoulders is nuts.and 'Not' a Cheng thing.
<<< In comparing photos of Cheng Manching and Yang Zhen Duo side by side, the former, to me, looks like he is reserving his power and sinking vertically down between his hips, whereas the latter looks like he is expanding as far as possible. Do you both see this differently?
<<< Well yes and no, let's start by saying that what Cheng's does in the finish posture is to Square is hips and YZd does not , at firsts I thought that that might be a
Cheng's thing but then I saw Yang Zhenji, square off when he did his postures. so I then I thought that Cheng's the only one who bends is leg , but then I saw Tung Hu-ling and his father also having their back leg bend, see http://www.ttopa.com/thl.htm
and on the same site look at YCF dressed in white doing brush knee is
back legs is slightly bent, hes hips are squared and no angular and loosk more up right then the so called leaning posture from his youth . now Audi im not making any conclusions just observations , and on a side note. Cheng tought to first shift with the back foot straight (Not Locked mind you ) and then when you square off your posture to bend the knee.