I'm having the same issue as the prior review, i.e., can't get the mount tight enough to keep it from smacking into the roof when at freeway speeds. I'll try his mod of harnessing a bike tube.
Also, be careful of the wheel rotation stop addition and how it's positioned when driving, particularly without a wheel mounted. Make sure the opening of the stop is facing towards the back of the car otherwise it will eventually (pretty quickly in my case) snap off from continuously flapping back and forth from high and fluctuating wind turbulence. Might have said something like this in the directions, but it's lame design imo.
2011 vw Jetta Sportswagen