The trademark filings came first. In May 2025, Porsche registered the names « Flachbau » and « Flachbau RS » and said nothing, leaving enthusiasts to speculate for fifteen months. On 14 August the company finally showed its hand: a one-off, road-legal build from the Sonderwunsch department, based on a like-new 2018 911 GT2 RS with the Weissach Package.
The customer’s brief fit in a single sentence: even more performance, a slantnose look, and a rear wing in the spirit of the 911 GT3 R rennsport. Nearly three years of work followed, shared between Sonderwunsch, Style Porsche, development engineers in Weissach, Porsche Motorsport and Manthey.
The finished car wears a Grand Prix White developed specifically for this project and matched against a historic 911 from the Porsche AG collection. A U-shaped contrast graphic on the bonnet, inverted compared with the standard GT2 RS stripes, quotes the Martini livery of the 935/78, the long-tailed Le Mans racer the paddock nicknamed Moby Dick. Grant Larson handled the design despite having retired; the American had already penned the 2018 tribute 935, built in a run of 77 cars with 700 PS.
Low wings, stacked lights
The front wings sit lower and carry slatted louvres that vent the wheel arches. Round headlights gave way to a stacked arrangement of LED units: just under four centimetres tall for the low and high beams, less than two for the daytime running lights. The front bumper is entirely new, the fuel filler flap and its mechanism were reworked to follow the flatter wing line, and subtle black Manthey flaps tidy up airflow at the front end.
At the rear, the wing rides on S-shaped mounts inspired by the 911 GT3 R rennsport, raised by about five centimetres here. It adjusts by hand across three positions, a patented arrangement, and in its most aggressive setting produces 554 kilograms of downforce on the rear axle at 340 km/h. Depending on position, that is two to three per cent more than a GT2 RS fitted with the Manthey Kit.
Weight came out everywhere. The build sheds 31.6 kilograms from a car that had little left to give. The PCM infotainment made way for a leather-trimmed storage bin, the audio system went, and so did most of the sound deadening and floor covering. Behind the seats, bare metal painted Grand Prix White replaces the trim, while a newly laid wiring harness runs exposed, stripped of redundant wires. The warning triangle and towing eye, mandatory for road use, live in a removable emergency box that stays in the garage on track days.
Tested like a production car
Porsche built three test vehicles for the programme. Digital crash and airbag-deployment simulations came first, then CFD work, a hydropulse rig and static sandbag tests for the wing, followed by wind tunnel and lighting tunnel sessions, test days at the Mendig airfield and 50 laps of the Nürburgring Nordschleife. In total, the wing absorbed loads equivalent to roughly 150,000 kilometres of customer driving. « On the Nordschleife, it becomes immediately clear how cleanly aerodynamic concepts work, » said test driver Lars Kern, describing a car that stayed « extremely stable and precise even at very high speeds ». When a camouflaged test car lapped the Ring, footage passed 100,000 views within a few hours.
The car sits at the crossing point of two Porsche traditions. Slantnose 911s and special requests have been intertwined since the 1980s, when the factory sold 948 flat-nose versions of the 930-generation 911 Turbo between 1982 and 1989; they remain among the rarest 911 variants today. The 935 that inspired the whole exercise won the World Championship for Makes four years running and took victories at Sebring, Daytona and Le Mans. Manthey, Porsche’s technical partner on the build, adds its own credentials: seven overall wins at the Nürburgring 24 Hours, six class wins at Le Mans and eight FIA WEC titles.
« Our aim was to reinterpret the iconic look of the 935 without compromising on safety, technology or road legality, » says Alexander Fabig, who leads individualisation at Porsche. One customer gets to enjoy the result. For more context, see our English report on the museum-livery 718 Cayman GT4 RS Clubsport that raced at the Nürburgring this month, or our French-language archive on Porsche’s turbocharged lineage and the rarest Porsche models (both in French).
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