Thanks! Whoa, you already got past my favorite part which was getting the shape from the block of wood! Btw, it looks same to me:
And here are the measures I ended up with - the top part (kou) is 68mm and measuring from the same spot on top to the bottom of the tenjin, 195mm. About the curve… I wish some kind tsugaru owner would just trace down the side of their shamisen and send it to me so that I can sleep better 
Anyway, nice work! Can´t wait to see more! 