RE: V-Tail Incidence
If the vtail saddle is parallel to the wing, you will have a negative incidence at the tail (assuming your fuselage tapers.) The vtail saddle should look like it has a noticeable amount of positive incidence. You have to account for the v-tail falling deeper into the fuselage as it widens. It is like the old toy where you slowly moved the steel rods apart to get the ball to roll uphill.
Kurt