I agree with pianotuna.
I don't do it every time, but I usually take a lap around my storage yard to visit the few rigs that use covers. None of them ever last a year, because the wind whips them to shreds. And the RVs are more beat to hell than any of the other rigs in the lot.
I'm willing to admit that all these covers I've gawked at over the years were installed incorrectly, but that also means that I've never seen anyone who knows how to do theirs right.
I guess that means that I agree with pianotuna AND grit.