I sense that there is an emphasis on position of elbow and spear.
If I remember correctly Wu Zhong learnt Baji before spear, so the i really question the idea Baji based it’s power on spear.
The postition of elbow depends entirely on the usage of the elbow and the movement is not static.
So 肘、頂、擠、肩、靠 etc are all very different.
Common error
1, Stance too wide too low, should be about width illustrated by 李元智
2, No stomping, although some say you use it to accelerate but you really don’t need stomping for acceleration
3, elbow too straight when punch, or shoulder over extend when elbow or elbow raises too high but no defense to the armpit
4, Lack of practice on punching bag
5, With spear partner drill there is a big interval delay between each thrust, the frequency or beats of rhythm should be higher.
Finally most people can’t differentiate the force difference between Pigua add Baji, and Baji add Pigua. These two are not the same.