Timbo, reading that again, you wouldn't save any weight if you use the same lay-up.
The idea with carbon is that, for instance, if you were going to use a 600g/m2 glass cloth, you could replace it with a 400g cloth [or even 300g].
In addition to saving 2-300g/m2 in cloth, you would save the same again in resin.
Sounds good until you see just how thin a 300g skin is - not very practical on anything other than an A-class