Neil Pryde old Vitesse sail, flextop masts?

I have given up on shortboarding am back to longboarding. I had a very good deal on E-Bay for an old Neil Pryde Vitesse 6.5 sail.( $ 50 !), brand new, still in the package, with the warranty and instructions. Looks very cool! It must be from the 80’s or 90’s! The luff is 470 cm and, surprisingly, it goes with a very wide boom ( 240 cm)

I’d like to rig it on my current mast which is a 460 cm constant curve mast( Gun Sails 55% carbon), but when I tried it inside the luff pocket, it does not bend as easily as with the other newer sails I have. Actually, it is very hard to even start DH manually and there is a deep vertical crease from top to bottom of the sail. I don’t know if it is because it requires a flextop mast, does it?
I’d be surprised, though, because in those days most longboards took stiff aluminum or fiberglas masts and I don’t think that windsurfing knew all the niceties of modern technology .
Perhaps the problem is that I didn’t do the complete rigging as I would do on the beach(we are 20 below here!): I only slid the mast inside, but I didn’t attach the boom because there is no room inside my house. I’d appreciate your comments.

Thanks

Francone

If that thing is what I remember from the early 90s it would have taken a glass mast with a lot more flex than most things today. It would also have taken a lot of outhaul to pull what shape there was into it.