In Shamisen of Japan, Kyle mentions somewhat briefly that the sao should have a 1mm curve lengthwise in the fingerboard. Like any stringed instrument this raises the upper neck above the lower to give the center of the string room to vibrate.
I’m laminating a fingerboard on the sao so in order to achieve this, should I sand 1mm curve into the sao before gluing on the fingerboard?
I am using a carbon truss rod 8mm square so my thought is to set the rod in 9mm deep and sand the mid sao to taper down to it, then back fill the 1mm or less gap with epoxy, sand flush and then laminate the finger board to the slightly curved sao.
Does this make sense? Or and I overthinking and overvaluing 1mm of 1/4" fingerboard?