Been working on it little by little over the last few days.
Pic 1) The insert after a lot of filling and sanding with a shot of paint to see how it looked.
Pic 2) The insert installed with a lot more filling and sanding around the edges to make it blend in to the fuselage.
Pic 3) The unmodified kit part for comparison
Pic 4) Tail planes added and the bottom shot with MM Azure Blue