Definitely add the stiff flaps behind the tires but don't add the full stiff flap at the rear. That's what causes rocks flying up. We've seen the damage done in Whitehorse Yukon on our Alaska trip. We just had the individual tire flaps and got no damage traveling within minutes of two motorhomers driving the same road. When we all pulled into the campground, they were already removing the across-the-rear flap. Large stones were laying at the base of their windshield from the construction area. We had none and absolute no damage on the Alaskan trip or for 8 years in that motorhome.