There can be no disparity of command issued to the body. The strength of Pi Chuan is imparted mainly through the waist and intercostal muscles. The half step of the feet does not vector power in Pi Chuan as it does in some of the other elements. The kinetics are simply not there to apply vectored force. Rath er, the half stepping in Pi Chuan should be applied in synchronicity with the arrival of the body's center at it's pre-determined spacial point when the actual blow is delivered, thereby maximizing the body's rooted connection to the ground.
More solidity means more potential power.
Lastly, power originates in the waist, is rebounded through the legs, developed through the torso and manifest in the fingers. But Hsing I has been best likened to a whipping piece of rattan. It moves at once in a brisk wave. When practicing, remember to lead with the hands when performing Pi Chuan and connect them to Tan Tien so that the whole body moves as a unit. If you think of leading with the waist, you will move too sluggishly.