Oh forgot to explain what they are!
If you look carefully near the rear of the boards, you will see the slight wings near the tail. On the Starboards they are very close to the rear and very sutble. Some good images on the I sonics here.
On this link you see an old Mistral with them. I think the idea was to provide area for planning, but once up to speed the narrowed tail added control. Also perhaps the thin wings provide "bite" during gybing?
Anyway just got in from cleaning up my new classics, something LeeeD would be proud of!
I've just inherited a 8.4 Hi Per Tech and a Mistral Eruption, which is like new! Will be interesting to try them out and see how they stack up to the modern stuff!