It has been many years since I pulled a 5 th wheel on the Alaska Hwy but I don't remember any damage done to it. I always kept a set of mud flaps on my truck. I have talked to folks in 5ers that report the brush, full width guards do well. Have also seen some that have added some diamond plate aluminum across the lower front area. Plus those that prefer plywood, bubble wrap, cardboard, etc. with my present 5er, don't believe I would add anything as the lower front is some type of molded poly material and appears to be very hardy. But on my current truck, I have individual mud flaps on front and rear tires and wouldn't expect any serious amount of gravel to hit the front of the 5th wheel.