I regulate the curvature and convexity independently for each string, based on the expected usage of the instrument.
For my fingerboards, I like to choose between a half dozen different types of wood, each one with its own diverse characteristics. I mainly use the following woods, in this order:
I carve fingerboards to measure, exactly in the shape my client wants. I offer many possibilities, such as fingerboards with three octaves or more, with cutouts at the end and with position indicators.
Ebony is a more traditional choice, and nevertheless continues to be almost always the best option. The sonority of ebony has proven to be superior to the vast majority of other woods, and its finishing is perfect.
There are situations, however, where it does not achieve the best result. For example, in instruments of inferior quality, it may prove to be too wasteful. This is because of its weight and density. When an instrument does not have a great resonance, any additional gram may harm it even more, and in these cases an ebony fingerboard ends up becoming a problem.
Purpleheart is an almost perfect substitute – it is a bit less dense. Thus making it an excellent option for less expensive instruments, and also for other instruments which require the solution of a resonance problem – I’ve shown that sometimes wolf notes may be diminished by using this wood. Purpleheart also allows for a perfect finishing.
I would say that Bahia Rosewood is my luxury option. Since it is a wood that is practically extinct, it is incredibly difficult to find. I have some boards that are up to 200 years old, and I believe they are the only ones of their kind that I will encounter over the next years. It is also a difficult wood to work with. It is a lighter wood than Ebony, like Purpleheart, and furthermore may be used on almost all instruments.
Both Ironwood and Ipê Tabaco are options for less expensive instruments. Neither one of these woods fully satisfies me, either in its finishing or sonority, but I consider them reasonably appropriate.