Xue Sheng
All weight is underside
ok I'm trying to catch up on Santi shi and from my google search, pictures and videos that I have found, those same movements are in the TTCS xingyi set... But as I don't know much at all about xingyi yet as I have not taken it at this point in time I may not even know what to look for. I take xingyi for a week training in June. I was told that while learning xingyi that certain movements are done repeatedly (much more so than the other forms) to train the body and mind on how to correctly do them and even held still for a time to build that strength... Again I don't know much about it but this is what I was told by different people. Additionally, some that I spoke to said that they strive to hold certain positions for 30 minutes.... perhaps this is what is being referenced?
Santi Shi
Click the above link that is santi shi and yes you will see that in many forms in xingyiquan but doing that in the form is not training Santi.
You need to get in that position and stand in it and NOT move to train it and Xingyi without that is, to be honest the only word I can think of is, floppy. Meaning to loose and limp there is no root and no understanding of application and without Santi Shi training there is no internal either