What if you had a central section (lights and plate mounted on it) that would be tapered. THIS would extend straight back inside the outer shell that would be hinged to be somewhat flexible. The center section would ride on rails.
I'll try to draw a photo to help illustrate what I'm talking about.
Ok, that didn't take long. This is a TOP DOWN VIEW.
Retracted for parking and maneuverability:
Extended 12":
