You can really only cover over the vents with plastic. And only leave the car cover on while it's sunny. When it rains, it would be better to take the cover off. Hot/wet days under a cover will kill the car in under a year. You MUST air the car ASAP after rain, because all 1200s leak I reckon

If the car is in good nick, it may last up to 18 months before the rust starts showing. I had to leave my old 1200 in the weather for 2 years, I had it under 2 different car covers, and that's why I had to start my new project. It basically died of loneliness under the car cover.

The first cover (~$90) disintegrated over the first summer.