I've had tow now and they both been on the door so I thought at least if you could protect the door you've gone a long way to stopping it.
If the guards were not as deep and made of rubber which is magnectic backed, think they wouldn't look that ugly while you parked up. In theoerty they prob only need to be 1cm deep by 4cm high and run the lenght of the door. They could even have a tapered of end to make it look a bit more stylish.