Oddly, it got a lot easier, conceptually, for me to understand the concept when I stopped thinking of it as moving relative to the ground in the same direction as the air, and started instead thinking of it as moving relative to the air in the opposite direction as the ground.
And ThinAirDesigns, you guys really need a better acronym. “DDWFTTW” (I presume that’s “Driving DownWind Faster Than The Wind”?) doesn’t exactly trip off the tongue.