First off, this Thread is about
MY Neck of the Woods and not some other brands or ways of building. I will not discuss other brands or build styles here. I do what I do and will tell you what I don't do what I don't. Or, is that why I do do what I don't? English Professors to the rescue?.. lol
On Wood properties and the 'whys' and 'why nots', I will compare Maple and Walnut for you as Neck Wood Candidates.
A Neck must have in my opinion some flexibility and some natural shock absorption for safety as well. Maple is strong and hard as well as flexible to a degree. If dropped, it might absorb the hit and just dent but in weak areas and bad falls, any Neck can be broken. Walnut on the other hand is a quite a bit lighter and less dense. It is also equally not as strong when it comes to absorbing hits or bends. Walnut is more brittle than Maple overall.
I have TONS of Walnut in stock in various thickness that would easily make the specs for Neck Billets. The wood I have was mostly air dried in the building and ranged from 6-10 years old on average. Great acclimation for a musical instruments except for one problem. Maple works better, period.
I am sure that if I made some Walnut Necks they would work but I have seen our Basses from even the 1979 batch with all kinds of dings and hits. Would Walnut take as much punishment? Would Walnut be able to be carved as thin? Can you have such little wood in comparison behind the Truss Rod route in the back center and not loose sleep if it was made strong enough?
I can make a Neck out of Pine if I like but it wouldn't be the best I could do. One of the hardest woods to find is white hard Sugar Maple in big clean pieces and free from defects, stains and knots and in various thicknesses and without distortion in the lateral growth rings. Walnut? Can you see the defects in this dark wood, its needed straight grain? Maybe not. Dark woods and dark finishes can hide a multiple of sins in woodworking and overall quality? Can you hide anything using transparent finished white Sugar Maple? Nope! No where to hide even a pimple in a Maple Neck.
The Maple I use has been in my building for many years with some of it from last century. I prefer to go with what I know and repeat proven results rather than to gamble with YOUR money. If something goes wrong down the road, it becomes MY money that gets affected as well.
We do what we do, bottom line..
For Fretless or any other Neck, the Fingerboard adds the Strength in. That is why we mainly use the highest quality stable aged Ebony for our Fretless Basses. We even use thicker stock to make up for the Fret height, and fretting strength that is missing on a Fretless. This in itself can help save a Neck over time.