The crank is one of the most complex parts for aerodynamics; the leading edge of your shape becomes the trailing edge 180 degrees later, you have the major influence of the forward speed and the minor influence of the rotational speed, your feet spin by, the frame is right there, the chain runs over the chainring and can’t really be changed aerodynamically, etc.
Our best aero shape was a knife-like 12mm wide at the pedal, significantly thinner than anything else in existence (cranks are usually 15-17mm at the pedal end). In the other direction, our desired profile was much deeper than usual.
The transition to the spider is another headache area. For structural and stiffness reasons, we want the spider to be integrated with the crank arm and fibers running through both. Yet we also want the chainring to be separated spatially from the drive-side crank arm (not one blended shape) to avoid aerodynamic blockage. The Torno spider offers exactly that and works in unison with the dedicated Wolf Tooth aero rings.