Very roughly speaking, .005 m^2 in CdA is small but not teeny: it's roughly equivalent to the area of a standard business card. Flapping jackets are way *way* bigger, as are aero bars vs. being on the bar tops or hoods. In terms of wheels, a 15mm increase in rim depth (for the same rim profile) might be in the ballpark of 0.015 m^2; a reduction in spoke count of maybe 2 spokes would be around .01 m^2. [Edited to add:] Years ago I was testing on a warm day and the zipper on my jersey was a bit down -- not Thomas Voeckler kind of down, just down around the bottom of my throat. On a whim I did a test with the zipper all the way up. The difference was close to 0.01 m^2. That was so shocking that I returned the next day to repeat the test. It turns out that the jersey wasn't flapping around and the slightly lower zipper wasn't turning the jersey into a parachute -- the looser zipper allowed the jersey to bunch up and wrinkle around my neck and shoulders.
The point of the calc is that even 100g of mass (which many riders think is huge) has a small effect compared with small differences in aero.
Last edited by RChung; 10-19-22 at 03:05 PM.