Mix together, sugar, cornstarch, flour and salt; gradually stir in milk and cook over boiling water 10 minutes, stirring constantly until mixture thickens. Stir a small amount into slightly beaten egg yolks, then gradually pour that into thickened milk and cook about 2 minutes, stirring constantly. Add butter and vanilla and cool slightly. Slice bananas into baked shell and top with filling. Cover with meringue beaten with 6 tablespoons sugar. Bake at 350° for 10 to 15 minutes. Serves 6.