It seems to me that a guitar top works best when there is a sort of 'balance' between the stiffness of the braces and that of the top plate. There are various ways to check this, such as by deflection mapping, either by 'feel' or measurements, or by 'tap tones', listening for 'clarity' and sustain, or by Chladni patterns, and probably others too. In any case, the usual way to achieve this is to shape the braces to work with the top, since the density and stiffness of the top can vary from point to point in ways that are hard to measure.
CF doesn't carve very well...
One of my students got interested in using CF to optimize his top some time back, and we made up a few samples with vertical laminations to check out. The carbon layers were thin, and didn't add much stiffness, and we realized that the braces would be hard to work with and 'tune' so we dropped the idea.
The brace setup that the OP shows is the same basic one that Smallman uses. It's a sort of I-beam, where the 'flanges' are CF and the 'web' is wood: balsa for Smallman and spruce here. The stiffness of the brace is determined largely by the cross section and material properties of the flanges, with the web only being there to maintain the proper spacing of the flanges. With that sort of brace you can't change the height without losing the CF flange, so there is no (easy) method of fine tuning. All you can do is either add mass or restrict the area of the top, both of which work against what you're trying to do with that brace construction, getting the highest ratio of top Area/mass with sufficient stiffness.
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