This is a good idea. You could start with the entire enlargement and then reduce it by and by, to see how much is needed.
Do you glue the stabilizer onto the fuselage?
I just glue a wire in the 2 mm throughgoing carbon tube and bend it on the bottom side of the fuselage to fixiate it.
So I am able to easily exchange the stabilizer.
And, if possible, start testing without winglets.