The issues with grill covers is that there is no clear plastic to see the tail lights of the RV and it's not closed at the bottom to keep dirt, water and road grime off the most critical bits of a bike which is the drivetrain.
I've had this one for 3 years now and it's just starting to look like it needs replaced. Not bad when you consider the cost. It covers 2 road or mtb bikes, easy to put on and off and zippers closed so it gets very little under spray and no road grime on the bikes. It also has plastic windows so you can see the tail lights of the RV. I have some pretty expensive bikes (most are a few thousand each) and this cover protects them just fine.
Bike cover