Peng can be either palm-in or palm-out.
When it is palm-in, the hand is closer to the body. The palm rotates up and away from the body. The arm spirals outward.
When it is palm-out, the hand is further away from the body. The palm rotates down and away from the body. The arm spirals outward.
Be careful not to lift the elbows or affect the shoulder joint.
Note that in order to maintain open elbow kwa, palm-out is further away from the body than palm-in.
