As I understand the paddling technique: 1) you plant the paddle forward with your right arm, 1b) your right leg is bent at the knee and 1c) your right hip is rotated forward by your straight left leg pressing against the left peg. 2) While pulling with your right arm and 2b) rotating your right abs sternward you are also 2c) straightening your right leg by pressing against the right peg, 2d) and allowing your left leg to flex which rotates your hips (and the seat). 3) Repeat on left and alternate left and right until race is finished. 4) A rotating seat that pivots around a vertical axis facilitates the hip rotation.

I stole this idea from Ted Van Dusen who incorporates a rotating seat into his Mohican and OK1s