I've got a question. I just bought a new arrow gtr .21 v3. It comes with an extra shim in the box. The manual says to put the shim on the motor for the first 1-2 gallon or install it after the break-in process. This seems confusing to me? I searched through this forum and saw the most use the shim only at the break-in process and after that (when mech. pinch is almost gone) remove the extra shim and leave one silver and one copper/brass. Can someone verify this is the right thing to do? Thanks