This isn't really a new building technique, I've just tailored standard composite construction techniques to my particular needs. There are other ways to build it though.

I considered carbon chainplates but like Wayne said, too concerned about cracking them. I have however used carbon to attach the forestay bridle rings (triangular rings) to the hull. I've also used carbon as a backing plate inside the hulls at the chainplates and the rudder pintles. The laminate will be de-cored and the hole filled with hard bog where the bolts go. The beam mounts are also carbon for stiffness.

You're right, there's no point building lighter with carbon. However, there is a point in building to a similar weight to glass construction but with much increased stiffness. This is more important from the forward beam to the bridle attachment than anywhere else on the hull. Increasing the stiffness here will directly increase your boats ability to hold forestay tension, which will improve your pointing ability.

This however isn't the only thing that affects rig/forestay tension, the forward beam stiffness will have a huge impact on it as-well.

Weighing up the benefits of potential money sinks is a tricky task. I have decided that carbon mast and beams will be a better investment than carbon hulls. If I had money to burn, carbon everything would be the go.

PS. There's other design alternatives in the hull laminate to increase the global stiffness of the hull platform, in my opinion anyway. You may notice it in the photos. A hint is to think about the hulls with beams attached with the rig trying to twist the hulls.