I'd have to agree with the grass skirt units. I had a basic one and it really did a great job keeping the bugs off the lower end, but it didn't do a great job keeping rocks at bay.
I've mounted actual rubber mudflaps onto the chassis of my tow vehicles and also use the Enkay as a last ditch effort. I know some folks consider dings in the front beauty marks that come with age, but I like to keep my Airstream as young as possible for as long as possible.
My suggestion would be to seriously consider actual mud flaps and adding an Enkay. Reason I say this is that I found that as good as the Enkay is, depending on your overhang, the Enkay can have it's limitiations in protecting against nearly all possible projectiles coming off the tires. I found that adding actual mudflap that are neary 3/4 down the tire footprint, along with the Enkays provides what I would consider an excellent barrier to the trailer. I've taken the Safari now on about 3-4 trips where it was really nasty gravel roads (and keep in mind I have the off road tires that came from the factory on the Suburban that pick up a LOT of things in the treads) and met my parents up at one location with similar roads. Pops put on the factory OEM flaps on his Silverado and I installed my modified OEMs on the Burb with the Enkays. His trailer was covered in mud, sand, and had a few dings, where as the Safari had just water mist on the front....granted dirty mist, but no dings, dirt or sand.