Page 633 from the November GCR, section 9.1.5 in the PCS
a. Modifications
1. The body, unibody, frame and their components can be lightened, provided that structural rigidity is not compromised
to the point of requiring additional support. No nonstock openings can be created in the bodywork. The lightening
of the cars structure can not create any openings into the cockpit, or from the wheel well to the engine/trunk
compartments. Existing seams in the unibody and frame can be welded.
2. The hood, hatchback, deck lid and fenders can be replaced by components of an alternate material, provided their
appearance remains stock. Factory bolt-on fenders can be replaced in their entirety. Cars with non-removable fenders
can replace the front fender panels going forward from the foremost door opening and the rear fender panels going
rearward from the rearmost door opening. Replacement components of an alternate material may not extend into
the roof structure of a closed car above a horizontal line placed at the lowest point of the driver’s door window
opening.