You realize this experiment has been done hundreds of times and always turns out the same.? People measure a change in drag in a wind tunnel, convert that to a change in CdA, then do field testing to see what the observed change in CdA is. They may not have done it where the change in CdA comes from shaving, but they have done it for all sorts of changes and always find the field test pretty much aligns with the wind tunnel results.