The Aero Car has drilled axle slots so your car rolls straight while conforming to all rules. Includes pre-drilled 3/8" weight holes for tungsten cylinder or zinc round weights. Also includes holes to (optionally) raise either front wheel to reduce friction.

This block weighs 1.3oz +/- .2oz so it needs between 3 and 3.6oz of cylinder weights. Just insert weights and fill unused holes with wood filler.
This is a BSA block with axle slots that conforms to all Cub Scout rules.