Limiting brushwork to Wei and Jin Dynasties is not a matter of using a pen, but a matter of structure, which originates from the heart. Tightening the middle palace and stretching the limbs is the most natural and comfortable way to write. The way to write this structure with a pen is to use a pen in Wei and Jin Dynasties.
This kind of structure in which the middle palace tightens and the limbs expand is also a natural structure that Li should have when he changed the eight-point regular script. After the official script is stretched, it naturally contracts and stretches its limbs. This is the key. This so-called Jin and Tang brushwork should also be the only regular script brushwork in the future, so it is not easy to use a pen through the ages.