Dude i wouldn't worry about it. If it was that much of a hassle no one will be driving sports cars. Yes you do hear alot about sports cars getting stolen, keyed etc, but the thing is even crappy cars get stolen, you just mainly hear about the nicer cars though.. plus reading a Skyline forum, you're gonna hear alot of things happening to a skyline.
I'm sure most members on this forum haven't had anything happen to their cars.
Well i haven't had anything (touch wood) and i live near Cabramatta... oh actually i got my valve caps stolen once when i parked at Cabra.
Sometimes you worry about where you park it etc.. but the joy outweight the woes!!