You could always buy a F16 now with the knowledge that you could beef it up to fit into the 104 class, its called hedging your bets.

My bet is that once you had a F16 you would not consider the 104 class as it would mean you would have to cart another 15 odd kilos up and down the beach and you would have to dumb the whole package down to match the other less competitive boats. Mind you starting off with an F16 would be one hell of an advantage as you could ballast it in all the right places.