Eric,
Regarding carbon beams:-
Of greatest importance is the cross sectional dimension of the beams and how beams are attach to the hulls. Believe it or not this is more significant than if they are made of carbon or aluminium.

An interesting point is the greatest benfit came from carbon beams in the A class when they started gluing the beams to the hulls.
But with a 10ft beam that is not such an attractive option as you have a monster that can not be broken down to store in the off season.

We have focussed on the key aspects of tortional stiffness when working on the Blade F18 and developed a system that provideds a platform 4 times stiffer (in tortional) than other F18 platforms that we have measured.

It is my personal view that anyone paying for carbon beams and not gluing them in or doing anything special to attach them could be just buying bragging rights.

BTW:-Macca's beams are aluminium.

This is just the way I see it.

Regards,
Phill