I believe the elliptical wing tips are easily removable and a wooden fillet added instead to clip the wings. All of The Fighter Collection's Spitfires (MkV, MkIX and MkXIV) had clipped wings but the Mk IX sported elliptical tips during the filming of "A Piece of Cake". Early MkXVIs were high back, they were essentially MkIXs with a Packard Merlin.