Four
I did my plane in vinyl, but I'm no expert. I think recognizing your limitations is important. By that, I mean, breaking the application down into smaller pieces to have a better outcome.
Make no mistake the compound curves are likely to make this a non-perfect application. If it was my plane I would do it realizing it was not going to come out perfectly and I would have to live with some small wrinkles.
A pro may be able to do this on one or two pieces. Looking at your pic I would plan on four. Even then, I know its going to be challenging due to the curves.
I would do one side first and split the vinyl longitudinally down the middle. I'd first lay 2 stripes of cutting tape on the the top, one for the first cut and one for the second side (or use triple tape). Also do two strips of cutting tape horizontally down the middle of one side, longitudinally.
Then try applying the top piece of the first side. For me, I'd be prepared to do this two or three times before I got it right. Good thing vinyl is cheap!
Once you get the first piece as close as possible the learning experience should help you with the following ones.
If you trying for show quality, that's another story... Then I would hire someone to do it - or paint it.