Lexus has done its best to get the most fuel efficiency out of its RX models , hence the 400 and 450H. Fuel Mileage is the key component and the engineers decided that there was a drag factor on the 450H that could be reduced. The elimination of the roof rack. I drive 120 miles per day for work and within the past week using the mpg numbers on the dash and driving the same road daily I have noticed and increase of 1 to 1.5 mpg using a 73-75mph cruise. The cabin is comfortable and I can not say there is a noticeable change regarding wind noise .
I would never have used the roof rack nor would I take a chance and put anything on the roof of my vehicle. Any mistake or scratch in the finish is a very expensive proposition at the Lexus Dealer, much cheaper to rent a pickup if I have to move anything at $39 a day,