Hey Scratchy, welcome to the board.

I have accelerator balls on a few of my bows, and the most speed gain I ever got from them was 5fps. Sometimes less. I know guys who claim to have gotten more, but I never have.

You can get the same results by putting 3 large brass nocks top and bottom. The only drawback to them is they are harder to move up and down looking for the best spot.

Good luck!