I also do not find any difference when the top is down except for the fact that the front windscreen causes additional noise in the cabin at highway speed.
However, with just the sun roof open and the front screen in the up postition, I do notice less turbulence at highway speed.
For the most part, if it had never been included with the car as OEM, I would never have missed it and would not pay for it if it was an option.




