>>>> I can hear the rear of the blade making contact as the piece is passing it. It is so slight, I can barely feel the difference.
That is perfectly normal with a well aligned blade. After all, the kerf is exactly the same thickness at the front of the saw as it is being cut as it is at the rear of the saw as the blade rotates through it. It's going to microscopically touch. In addition, the blade tips are going at over 100 MPH. The wind created will cause a slilght vibration to be imparted to the ZCI.
If your blade and fence are 0.002" or less, you are good to go.