I wouldn’t be concerned about drag either. As part of your application (Except if you’re driving a racing / trophy truck…) the drag established by any gentle bar irrespective of the place it's mounted on the car is negligible and won't influence MPG, major pace, acceleration or another driveability aspects. http://cars94814.bloguetechno.com/The-Basic-Principles-Of-Lights-On-Roof-Rack-21187578