A [very late] update: I finally finished my fretless bass with the flat fingerboard and it plays great! It's a bit hard to explain how it feels. It does somehow feel... flat, but it's not hard to play at all. A rounder board still feels more familiar to me, having started playing bass on a Peavey with a very round 8" radius, so I will probably stick with compound radius boards for the rest of my builds.
I have since created a parametric script to generate the G-code for fretboards, and just finished my CNC, so I can start creating all sorts of fancy fretboards now!
