neck pocket size?

on a bolt-on, the pocket should conform to the geometry of the neck as it terminates at the body. basically the taper of the neck comes to a terminus at the neck pocket.

you need to also have a small gap at the butt end of the tenon and the neck pocket to allow for expansion of the body and neck as they react to humidity changes. too tight and you'll have that typical spilt at the treble side cutout. a small fretboard extension in this area conceals the expansion gap very well.

tone wise, you'll want clean precise woodwork. the floor of the pocket and the bottom of the tenon need to be true and flat with no gaps for maximum string energy transfer. the neck should push in with your fingers with around a .005 to .008 air gap at the butt end. if you have to tap it in with a mallet it's too tight. when humidity changes and your woods settle in, it'll come down to body vs neck and the neck always wins -and you'll see that result with a crack in the treble side cut-out.

 

My general rule is that I like bolt-on bass neck pockets to be at least 3 1/2" long, for stiffness and structural strength. That's the "safe" number. You can build basses with shorter neck pockets than that, but you have to be careful with the thickness of the body wood under the pocket, body wood choice, security of the neck screws/bolts/inserts. The shorter the length of the pocket, the higher the load on the screws/bolts.

 

generally around 1.25 to 1.5x the widest portion of the tenon. body wood under the pocket: minimum 1x the neck and fretboard max thickness at the tenon.

fwiw, neck-throughs eliminate a lot of these concerns.