You probably won't be driving down the road in your park model, but the MaxxAire vents would still be beneficial. You can leave your vents open, and if it starts raining, not a big deal, the rain won't get in.
ALSO - They may offer some additional protection if you live in racoon country. Those little critters have figured out how to open standard roof vents.
They just haven't figured out how to get out once they get in