[dad911]

Weight in the back. Three wheels. Better quality graphite. Rub graphite where the hub touches the body, and on the body near the axle. Drill holes for the wheels on a drill press (or mill if you can get access to one) for a wheel alignment. Lengthen the wheel base will run straighter. Make slightly under weight at home, then add small screws to make it slightly overweight. Take out screws as necessary to compensate for official scale.