Drilling for New tuning machines

[Fendercustom7]

Hey, I just bought a 5 string bass neck and wanted to buy some black tuning machines for it. Unfortunately, there are holes drilled for 2-screw machines set on each side of the hole, and I am buying 4-screw tuning machines set in a square pattern around the holes.

Should I fill in the existing holes with wood glue? Should I put the bass in a vice before drilling to prevent cracking?

[Musiclogic]

If the tuners fit the existing holes, and you just need to delete the screw holes, use tooth pick ends and wood glue to fill these, then if you need to screw into or close to these holes, you have wood for the screw to grip without creating a huge hole that the screws fall out of. As for putting the bass in a vise, not really, if you mark the screw holes, and then keep the neck stable or even clamped should be quite enough, you only need to go about 1/8" to pilot in the screw