Has anyone used one of the racks which attach onto the back of the car?

Im aware of the plastic spoiler but has anyone used one of these for a temperary measure?

I have a boot mounted rack thats adjustable in all directions so ive made it clear all the panels and not stress any parts of the car. Sticks out abit above the height of the car but clears the lights and number plate.
 
Seems like Thule racks are more available in the UK... Yet Yakima racks are preferred by most in their home market. If it were me I'd try tracking down the SportRack Mondial system!
http://www.sportrack.com/a0230
Used to have one back in North America... Unfortunately I don't seem to see the aluminum one I had.:( They have great ratcheting fitments for a very precise secure fit. Then the Bike or other Accessory rack slide into a locking channel. Makes this the cleanest design on the market!
 
tow bar all the way:

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