It's a development that brings a smile to my face, and I'm sure aerohead's.
The concept would rely on very stiff, very light panels that have to meet very precisely over whatever it is, a 10" length? Rather than butt together as shown, if the gap scissored shut it would be better supported.
No trunk access so maybe open the doors like the Ford Evos:
OP -- What car are contemplating modding? Maybe extend the car 10" already instead of cutting into the existing body for the space?