I'm gonna try and make peace with this truss rod then :) ,shave a little off that 5th fret and pretend I never looked under the cover to begin with. ...

I just realized what I'm turning with the allen key isn't a nut but is actually inside a cylinder that seems to run the length of the neck. The outer ...

Thanks for the info and quick replies, much appreciated.I have another G-400 here and tried to recreate the problem with no luck, truss rod doesn't bu...

It's moving along the length of the neck. It can be pulled out until the nut reaches the angled opening to the cavity.