Hi Claire,
There is a limit to how thin the neck can be carved before the truss rods will bust out the back. In general, most of our necks average .9 inches thick from the top of the fingerboard to the back of the neck (easiest to measure with dial calipers with the strings off).
A couple of considerations: 1) the less mass in the neck, the more mobile it will be. This means that a smaller difference in humidity will affect the neck. 2) Cost. While the price of the labor to carve the neck is not so high ( about $150) to make the bass look nice again it will require refinishing, which averages $950. Without a complete refinish, the modification will be quite noticeable.
If you ever order a custom built bass from us, please note that custom neck carving is not an additional charge on most models.
-Mica
