How to turn a hardtop into a covertible?

If you are not concerned with a functional top you have a lot more room to fudge. You could build it as a true "roadster" with no way of closing up the interior. I have thought of doing just that with some kind of cheapo econobox car. I think a mid 90s civic with the top chopped off and fabric snaps around the perimeter of the interior for a tonneau cover would make for a decent summer car. And really it isn't any worse than the horrible things ricers do to them thinking they are making a hot rod.

It likely isn't worth the effort and then the car is down and non drivable during the process. Plus you will have more rattles, noises, and leaks.