FYI: Each bow setup is different as to where the STS will work the best. So play with it a little bit. Mine works the best touching the string.

The serving was important on my bow. The STS was causing my string to fray.

As for loss of speed...I haven't noticed any. In fact, I have seen people take off string leaches, etc. because they put on the STS. So that will add speed.

Good Luck!