The conversion company is called Peters cabrio i think. They made the full cabrio E21. There is a huge metal contstruction made under the car to keep the strenght of the body.
I believe if you search the forum there is a topic about a restoration of such a car.
Gr Peter V.
.Some say he eats nuts and bolts for breakfast, all we know is he is called the carburetorman.
BMW E21, 1981 320/6 Ascot Grau.
BMW E85, 2004 Z4 2.5i Sterling Grau.
BMW F25, 2014 X3 xDrive 2.8i Space Grau.