Anyone have any Pinewood Derby tips/tricks?

I helped my son win the cub scout troop pinewood derby three years in a row and latter helped my nephew win twice.

I would take the nails they require you to use for axles and spin them in a drill and file off any burrs under the heads and make the raduis from the head to the shank as tight as possible. I would spin the tires on an axle to make sure they ran true and would file the edges to remove any flash. I would also chamfer the center hole on the wheels on boths sides. The minimize the side to side slope when installing the wheels and use dry graphite as the lube for the axles.

The addtional weight to get to 5 oz's was installed into the bottom of the car flush and midway between the axles.

Paint general shape and stickers was left to the kids.