The Best way to fix this boat if you plan on racing it is to locate another hull. Every other way will add weight.
The way I would fix it is to cut a large (six inch wide by length of the top crack ) hole in the top of the hull.
debur the crack from the inside so that the forward portion lines up correctly, and any questionable core is cleared out. Take a high build fiberglass mat (I like the multi layered one with the spheres in it) soaked in epoxy and line the inside of the hull as far back and as far forward as you can reach.
then do a normal hole repair for the top.
Lots of professional repair advice on Boatdesign.net

Rob