OK you made me feel a lot better, I thought I was being compulsive. You know I can't remember where I read to use polyurethane glue, maybe in Melvyn Hiscock's book? I can't check, I had to give it back to the library. I have never used polyurethane before but I went to the hardware store and bought some, it was $20 for this tiny tube, wow I thought this must be good, I could have nearly bought an entire pointy neck from Guitar Fetish (the batch that the factory forgot to rout the nut position) for that. On the pack it had a broken cricket bat being fixed and it said all the right things like it being flexible, etc. Then I broke my golden rule that is always try new stuff out on scrap, and glued it in.
The truss rod I am using is a Gotoh brand with a steel box, and the box slightly tapers towards the side that sits in the bottom of the channel, so at the top there is about 0.5 mm space between the box and the wood on either side. The polyurethane glue did not fill that space, the glue was runny like model aircraft glue. After 2 hours after it was supposed to be set but the glue on the spreader was like old crumbly but sticky silicone. I was feeling decidedly uneasy at this point, so I decided to take the rod out, and do some more research. It came out pretty easily so, I think you are right, even though the glue takes 24 hours to reach maximum strength.
So I went with something I am familiar with, Araldite epoxy, and tried again. This time the glue was viscous and the leftovers went very hard but flexible and did inspire confidence.
This time I felt good about it, the glue filled the gaps nicely.
Close up.
In blokey speak, that ain't goin anywhere.
Trying the hardware out on my scrap wood practice neck, this was made from a piece of wood 1 mm thinner than the real neck.
Happy trails