I only ask as a stemmed thought from xdcx's post, if I recall he's quite short & light?, so figured that even though his w/kg will blow most out of the water with similar CdA to that of a larger rider on a flat course it wouldn't bear quite so much influence.
W/CdA isn't something I'm familiar with but am familiar with the principle that the faster you are moving then the increase in work required to accelerate is a diminishing return compared to that at a lower speed. Is this similar?
This is quite broad brush but fairly helpful:
https://twitter.com/xavierdisley/status/538269709939253248?lang=en
Assuming a perfectly flat TT course and two riders doing 300w, one is 70kg with a CdA of 0.2 and the other is 80kg with a CdA of 0.18. The lighter rider will obviously have a higher w/kg, but as his aero position is comparatively worse he will go slower. You can compare their w/CdA by dividing power by their CdA value:
A: 300/0.2 = 1500
B: 300/0.18 = 1667
It's mainly a useful metric when you're trying to trade power vs aerodynamics. Rider A for example could squish himself into a 0.17 CdA but can now only put out 280w in that position. However, divide power by CdA and you get 1647, which is a significant improvement over his original position despite making less power.
As a benchmark, Wiggins' hour record was reckoned to require a w/CdA of ~2,200.