Surely a luthier should be able largely to tell in advance how the guitar he is making is going to sound? And surely with graphite or carbon fiber tops, the maker should know exactly in advance, no?

If the objective is volume (and some above so imply) then it's simply a matter of how much the top moves - which is why banjos are so loud.

If it's a matter of tonal balance then its much more complicated and depends on the response of the forced vibrations in the top to the harmonics in the waves from each string which I'm guessing is likely to depend on localised stiffnesses and hence, largely, strutting. I think Breedlove are experimenting with some totally unstrutted tops, depending on a Bridge Doctor to control bellying, and it would be interesting to hear: I'd expect a big boom and maybe a lack of brightness - but I've never yet played a Breedlove that "spoke to me".

I have however played a guitar with an unbraced (I think) aluminium body - flat top, teardrop shaped and that was fairly loud but very mellow - something I suspect to do with the softness of the aluminium.

THenthere is damping, which will control the rate of decay - which is where I suspects (see above) laminated tops fall short. But if that is so what about Rainsongs - if it's the glue in the laminated top that makes the problem, the Rainsong top is almost all glue (or glue-alike) and I'm told they are both bright and powerful.