I bought 17T, 19T, and 21T Mod 1 pinions from Hot Bodies to use with my Grid mount. So far, I've only used the 21T with a 6S battery and 1800 kV CC motor, and it's crazy fast. Still has tons of power (will spin Road Rages from a standing start on rough concrete!). I imagine 19T would be a good starting point and should still be quite fast. I imagine it would handle a 21T just fine too.