This was modeled after the finger board that is on my 16.5 inch viola. This could possibly be scaled for different sizes/types of instruments.
Note: This is a fingerboard FOR a 16.5 in viola. The finger board itself is not 16.5 inches.
I had to print it in 2 parts because my print bed is too small.
I recomend printing with the flat side (side with the concaved half) down.