The rule of thumb for flywheel weight for a street driven vehicle is for the flywheel to be 1% of the vehicle weight; ie. the vehicle weighs 3200 lbs, the flywheel weighs 32 lbs.Most instances related back to me regarding aluminum flywheels on a Y for street use complained about having difficulty in getting the vehicle moving initially. The flywheel by being too light does not have enough stored energy in which to help the engine keep the rpms up and subsequently the engine will want to pull down too easily upon engaging the clutch. On the flip side, the circle trackers that used the aluminum flywheels loved them but they were not having to use the clutch to take off consistently.