It worked very well and despite what you might think about the clamp on method it was very solid. For my own sanity I attached to shock cords from the bikes to the roof rack to minimize twisting moments while in motion. The rack didn't appear to budge the whole drive. I drove about 35 km with it on today. Some highway, main roads and back roads. I was concerned about the bumps but it behaved very well.
For the hassle free aspect of this, the fold down and the fold flat features, it was very much worth the 50£ price and the 50£ shipping. Very easy to use.