I'm counting on only the mud flaps behind the RV tires AND that 3M Scotchgard Clear Bra (Paint Protection Bulk Film 6-by-60-inches) that I got from Amazon that covers the plastic headlight assemblies.
Put the 3M product on the headlights of my '01 Saturn which I bought specifically to tow. Its wedge like angular profile seems to me to be a natural protection against rock damage.
So far only 3500 miles towing but no windshield or paint damage. I did find a rock hit evidence on one headlight but the 3M minimized damage enough that I don't need to replace the headlight assembly.
My decision to forgo countless protective products came from years of reading threads like this one by people who've bought various products.