All depends on the construction. I can make a carbon fiber Hood
for you that will be just as heavy as the oem (it will look wonderful too, yeah right) its all in how much they use. Shitty construction will have lots of excess resin and cloth. High quality production will only have enough carbon fiber and resin to get the needed strenght. The reason why carbon fiber is the lightest is because of weight per tensile strenght, and composites get their strength from the directional tensile strenght of each fiber. The reason carbon fiber int used everywhere on military jets and such is purely a money issue. If you. look in the civilian sector people use it exclusivly if they have enough money.