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Here's a shot of the rear section of the car. Like I said before, everything on the inside of the shocktowers is tube frame race car while the outside of the unibody up to the wheel wells remains. The rear shock towers and part of the frame rails are still present. There is plenty of triangulation going on here like a race car chassis should have.
The rear subframe structure is tied to the chassis, roll cage, rear suspension, wing mount, and air jack. The factory Mazda rear end has an aluminum plate sandwiched between the body and rear cover. This is probably done for two reasons: to tie the wing mount structure directly to the rear end (probably because it is so cantilevered) and to increase the fluid capacity of the rear end. FD rear ends run extremely hot and are notorious for burning up gear oil and diffs on track without a cooler and pump. The GR FD does has a diff cooler located in the rear diffuser/bumper (see part 1).
Here's another shot of the rear end, bulkhead, subframe structure in case you are planning on building a car inspired by the GR FD.
Two titanium mufflers handle the muffling duties. Personally I think the GR FD isn't quite loud enough. A rotary should scream in all of its ferocious glory. The turbo is already muffling the exhaust plenty for a race car.
I'm not exactly sure how this wing mount works, but I cannot imagine a riveted section of carbon transferring the downforce to the bulkhead that appears to be bolted together from billet aluminum pieces just behind the rear subframe structure. There must be a structure inside of the rectangular carbon section handling the transfer of downforce.
The dry carbon rear hatch was not only ultra light, but the quality of craftsmanship is top notch. This is not a Chinaman piece with carbon cloth put over layers of chopped mat fiberglass and pounds of low grade resin. This piece was made using legit pre-preg carbon in an autoclave.
