What are the thoughts on putting a vinal top on a car not orginally equipt with one.

I really like the idea of doing my car in blue with a black vinal top.

I know alot of people have said it is not a good idea becuase they trap moisture.

Is there a way to treat the metal before vinal installation to prevent it from rusting.

I was thinking of using an urathane primer than base coat clear coat than installing the top.

Thanks for any advice