Unusual neck construction help

[JACKSON JS1XM]

Only thing I've seen for photos are graphite or carbon fiber implemented on both sides of the truss rod like this.

Carbon Fiber Guitar Neck Reinforcement Part 1

 

[pilotjones]

...
Even Balsa would probably work, or foam. The Klos carbon necks are foam-core.
...

Also, if I understood and remember correctly, Heiko (Basslab) uses a foam core (for the whole instrument) then dissolves out the foam.

 

[Keith Guitars]

Also, if I understood and remember correctly, Heiko (Basslab) uses a foam core (for the whole instrument) then dissolves out the foam.

That's what I recall as well. Ulrich Teuffel was doing something similar with a guitar body, but he developed an allergy to some of the chemicals involved and had to discontinue the model.
Also, Pete Swanson (Dagmar Custom Guitars) uses a CNC-carved foam mold as a scaffolding to build his 'houndstooth' guitar bodies, then carves/melts out the foam afterwards.
It's a viable approach, but it sounds pretty messy!

 

[Max Bogosity]

Too bad most (all?) epoxies don't work well at low temperatures. We could use an ice sculpture as the core.