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The Civic uses the stock steel door on the drivers door but all the other doors are carbon reduce weight.
The cage is a true bolt in and bolt together street style cage. If it were up to us we would build an inclusive weld in cage with a proper height cross bar, better side protection and have it go through the dash to mount as far forward as possible on the frame rails instead of bend around the dash and bolt to the floor. This would help with chassis tuning immensely and make the super fast car much safer. The weight penalty would be around 30 lbs. We are pretty surprised that many top Japanese builders seemingly will ignore chassis stiffness but do elaborate seam welding and gusseting of strange locations on the unibody. On this car the front part of the chassis has been seam welded in select areas. 
A tower to tower bar is welded in place to stiffen the rear portion of the chassis.
A simple strut tower brace and some seam welding are the sole concessions to chassis stiffness in the front of the car. The minimalist approach to stiffening contributes a little to the car's feathery 2295 lb weight. This is impressive for a late model car since newer cars have a lot more substantial body structure than cars of just a few years ago due to ever increasing government crash standards. You can see the pillow ball upper camber plate here. With adjustability at both the top and the bottom, a lot of flexibility in set up is available for the alignment.
The windshield is braced with this nicely fabricated cantilevered support. I am not exactly sure why it is in this place. Perhaps Japanese rules?
You can see the Lifeline fire extinguisher here as well as the Odyssey lightweight drycell battery. It would be pretty easy to convert this extinguisher to a full fire system. The empty brackets is where the old Nitrous bottle went. This stuff is located in the mid chassis where the passenger seat would be for best weight distribution.
No elaborate pedal boxes or dual master cylinders here. Just stock stuff with a larger brake and gas pedal. The brake pedal actually had to be cut down a little because Dai didn't like it for heel and toe action.
