Another possibility, if you can persuade the crane owner to allow it,
is to fit a "headache ball" to the cable about 20-30 ft above the car.
Probably the headache ball would be part of a hook, and you'd have to
add a second length of cable between the hook and the car. The idea is
that you free fall the cable, but that the headache ball keeps the
cable taut when the car hits the ground. The crane operator then needs
to stop the cable before the headache ball hits the ground. This is a
fairly common system and seems to work okay if the crane operator knows
what he's doing.

Chris