More importantly, the 9 Sport was of a unibody design. This meant that the car was not offered as a convertible, although a small number of 9 Sport convertibles were built, using the chassis of the earlier 8 Sport.
The 9 Sport was a monocoque design. This indicated that it wasn't available as a convertible, though a limited number of 9 Sport convertibles were manufactured using the chassis from earlier 8 Sports.