Am I correct to assume that countersinking the flap trailing edge is exactly the same procedure we did for the rudder? Countersink both sides, and don't worry that the countersinks will intersect slightly and enlarge the holes?
Yup! Same as aileron (which you should have done already if you followed sequence in instructions). I'm drilling them now. For the ailerons, I went with a slightly longer rivet (-4 instead of the -3.5) and will likely do the same for the flap TE.
