HuntingEd, I've found that placing some sort of plastic or vinyl washer between the STS and my riser seemed to help (maybe my ears just wanted it to?)
And you can fine tune your STS to both noise and speed by adjusting it up and down the string and by adjusting how far in or out from the string the rubber bumer sits at rest. The noise & sound produced will change as the bumper is moved from touching the string to away from the string.
I believe my 2 set-ups resulted in about a 1/16" gap between the string & bumper. If you look here you can see the washers, but the gap doesn't show up in the pic's I took-
