I built the "Sleepy" version and kept it on for almost two years before removing it. I noticed no improvement of any sort; less bugs, noise, better mileage, etc. All it did was cause me to jack my camper another 3 inches higher to get it on and off is all. It sorta interfered with my vision and really interfered with my dash cam mounted high near the rear view mirror.
But if you want to give it a try, please do so. If anyone is near Placerville, I have mine sitting out back some place and they are welcome to it.
Since photobucket got stinky about 3rd party posting of photos, I don't think they'll post here, but here's a link to them if you car to look what I built.
http://s361.photobucket.com/user/skipro3/media/camper/IMG_7868_zpsgjmwi6iw.jpg.html?sort=3&o=7
