No one’s actually tried to steal my Skyline yet (although I’ve only had it for a few months now). They do seem to like the valve vaps though. I’ve had a few sets of those stolen!
I think there is only so much that you can do to protect your car from theft. Mine's got just about every feature you can get in an alarm, but if someone wants it badly enough, they’ll just tow it away. It sux, but that’s reality.