Hi
That's not a 'thing' its the air intake for oil or water cooling. Not sure which but early spitfires were asymmetrical as one was smaller and a different shape to the other. I'm planning a picture of a spitfire buzzing a garden party and have been experimenting with making 3d mock-ups of paintings so I can play with the light and composition. Any chance of one of you donating a model that I can use?

My pictures are here if you are interested: http://keith.jones61.googlepages.com

Keith