What To Use To Fill A Large Deep Hole On The Back Of A Neck

[toner]

I have an SG where the neck was cracked near the headstock. It looked like it was a 2 or 3 piece neck after sanding it down (like on a bc rich oribanez where you can see the curved line where the wood was joined (around 1.5 to 2nd fret area on the back side of course). Well it cracked there and in the middle there is a chunk of the wood missing probably about half the length of your pinky finger and all the way to where you can see the truss rod. Amazingly the neck is not warped or anything and still plays really good.

I want to fill it in (probably have to put something down in there first because of the truss rod, maybe a thick wax like that i can spray down in there with a red guidance nozzle/tube like cosmoline for rust proofing the insides of car panels, that way there whatever I fill it with wont bond to the truss rod? something else to use? I don't think wood filler is strong enough, Epoxy putty maybe?

I don't know what product to use that will remain at least as hard as the wood but have some flexibility for neck relief and future truss rod adjustments that wont crack up, because I plan on painting over it again. It's a set neck so I want to repaint the neck black all the way to the body where it joins in.

(I have previously worked as an automotive painter and have all the equipment for that part of it).

Any game plans/suggestions for me please? I have fixed and re-painted cracked necks before, but never had to fill anything.

[guitar2005]

Wax over the truss rod + epoxy to fill.

I've used wax on molds that I filled with epoxy and the epoxy came out fine.

[Mattia]

Here's a thought: use wood. And titebond. Which won't stick to metal.

[PTU 7's.]

Here's a thought: use wood. And titebond. Which won't stick to metal.

I did that on a neck that I was sanding and I reached to the truss rod. It works.