...you want to get really creative w/ weight?
Go to a local TIRE shop and pick up old tire weights...
Get an old cast iron skillet or something you can melt the weights in and create a mold in the shape of an area you want to mount the weight in your car.
Pour is, let it cool, drill it and your chassis in the location you want it.
Shoe goo it in position and run a flathead screw up from the bottom and nut and washer the top...IT SHOULD NEVER MOVE...
just an idea~