This guitar neckuses Carbon fiber as an exoskeleton with a lightweight wood core, such aswillow or basswood as a compression medium for the core. The finalouter face of the neck is a thin 1/32” veneer of hard wood. Therecan be as much as 200 pounds of pull on a guitar neck.

I've attached my design

Myquestion is do I have the design right? Where can it be improved?

I just commented on your 3D drawing, it does not seem to show a layer(s) of CF going through the "neck post" along the bottom/underside of the neck ..  You WILL need that to counteract the tension on the underside of the neck.

An open ended CF square box has very little compressive strength perpendicular to the box.  The same goes for expansion forces..

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