Daddio has the putty on his website for bout 5$, it is the best way to find the fast spot on your car once you have it built. If you newer racers will get your car weighted to around 4.90oz and then roll up a little ball of putty that will get the car up to the 5-5.049 legal weight, and just stick the ball onto the car in different places(provided you have access to a track), and without changing anything, make passes with the car until you find the spot that causes the car to go the fastest, then drill a tiny little spot where your fast spot is, insert the putty and wahlah. You'd be surprised what a huge difference .10oz is worth in speed when put in the right spot. Take care,
DG143