Make sure the rear mud flaps are properly placed behind the rear tires .. I don't believe your coach comes with a full rear mud flap .. but if it does make sure it's up high enough.. 6" they act as a suction device and at speed suck up the rocks and throw them at the toad. Their sole purpose appears to be looks ( they do look good) and advertising the coach on the Chrome strip.
What I've seen that does work well is something like "protect a tow " it's a horizontal net that covers the area between the coach and the toad with a bungie set up that allows turning. It keeps rocks from flying up into the car.