With the tentellones all in position I can now cut the sides down to the right depth. A Martin Triple-O measures 105mm at the end block and 85mm at the heel, so, allowing for the top and back, that’s where I need to be with my sides.
Using my trusty template, I mark out the depth at the neck, 1/8, 1/4, 1/2, 3/4, 7/8 and end block positions. Using a flexible straight edge I then join these positions together to form the datum line for the back. Then I carefully plane the sides down to the datum line.