Sorry to bring this one back from the dead, but I felt if anyone reading this, and bought the Thule one in the link- could ecounter the same issues I have had.
I have the same Thule one in that picture.
Although it's never fallen off, it's never filed me with confidence with it hanging off the boot & I never liked going above 60mph.
I did drill out new mounting holes for the bottom straps (to enable it to sit lower down- with the bikes behind the car instead of sitting higher than the rear window.)
I have broken two of the ratchet straps- they're made from really cheap cast metal & can break if pulled too tight.
Parts are easy to come by if you do break it- probably best to have a couple of straps spare in the car, 'cos if it breaks when putting it on the car before comming home- like it did for us, you could be screwed!
Also, one failed whilst driving
Which was a brown pants moment, when the bikes started to move about- luckily we were just pulling away from a junction & spotted it immeadiately(sp?)
In all honesty though, it was probably my fault- I did'nt like the way it fitted & was a bit heavy handed.
It did put light scratches in the paint where the rubber feet rested on the paint- but that's easily cured with some softer padding.
Plus the fact, they polish out easily, so no major harm done.
So as suggested, if we're going anywhere with the bikes now, we'll take a 'normal' car