Great mod! By "it's just a sliver", he means that the washer is just making the opening smaller "by a sliver", but enough to change the sound back to being close to the sound of the stock pad.
Brilliant! What is the diameter of the outside of the washer, and the diameter of the inside of the washer?
Imagine all of the "different sized washer mods" that are going to come out of this one lol!