Making my first bass from scratch, a medium scale maple and bubinga special. Got my truss rod today, a 23 1/4" dual-action jobby from Grizzly Industrial and see now that I have a problem. I think the rod is too long for my neck. Which brings up a few questions about these suckers. The guitars and bass that I own already have necks whose truss rods adjust from the headstock side. Given that the nut end of the rod is round, and slightly larger in diameter than than the rectangular portion of the rod, how exactly do I lay out the channel to accommodate access to the nut after it's installed? Also, what are some guidelines for determining the correct length of rod that should be used for a custom scale length? Is it nut to xxx distance from end of heel, or nut to fret N? Advice appreciated on this, thanks.