I use a 9502, and have never had any issues. as others have said, in tight areas if possible unload the bikes then reverse the car in so it overhangs into bushes etc.
As for locking it on I use one of those plastic locks on the clamp bolt, as had been said earlier, it could probably be smashed off pretty easy. But I have a cable lock that I use to secure the bikes onto the rack during transit (for peace of mind during pi$$ stops etc)
I tend to use that to lock the carrier to a lug on the underside of the car when I'm parked up with the bikes off.