Today I finished countersinking all of the auxillary and lower longerons, and angle stiffeners for the forward fuselage. I also rounded the corners of each of those same parts. To properly set the countersink depth for the lower longerons, which receive dimples from the sides of the 0.040 forward fuselage bottom skin, I fabricated an 0.040 coupon and drilled and dimpled it for #4 rivets. It took 6 "clicks" deeper than the #30 hole and dies as it did for dimples in 0.032.
This is how I stabilized forward fuselage angles for countersinking.