For the Head wind versus Tail wind, isn't it just that there is a difference in the overall aero drag at speed? Say you have a 10 mph headwind, that would be in essence the aero drag of 210 mph wind when the vehicle was at 200 mph. The reverse would be the aero drag of 190 mph wind with a tail wind at 200 mph. So there would be a 20 mph aero drag swing between the head and tail winds. Based on that, I would think a head wind would have a greater influence as the speeds got higher.