Wouter,
Both my Acat beams were $650 from Forte RTS. At that price why would you bother with aluminum beam on an Acat? Plus I can glue the beams on saving more weight, as opposed to build in fittings for bolting the aluminum beams down.

Plus I dont need a dolphin striker.

Lighter, stiffer, simpler, easier with Carbon beams.

My project came in at about $10k, thats including a $2500 Hall mast.

Carbon cloth for the hulls was $800, that was a 2005 price, but its no where near the majority of the cost.