Porsche and Manthey Turn a 911 GT2 RS Into a One-Off Moby Dick Slant Nose

In May 2025, Porsche registered the names Flachbau and Flachbau RS with the European Patent Office, and the 911 internet spent a year guessing. On Aug. 14, Porsche finally explained, with the car set to debut at Monterey Car Week. One customer had asked the factory to turn his like-new 2018 911 GT2 RS with the Weissach Package into a slant nose, and Porsche said yes.

The result is the Flachbau RS, a factory one-off from the Sonderwunsch department built with Manthey, the Porsche racing team based near the Nürburgring. Porsche says a team from Sonderwunsch, Style Porsche, Weissach development and Porsche Motorsport worked on it for almost three years.

A slant nose with a real pedigree

Flachbau is German for flat construction, and Porsche people use it for slant nose 911s. Porsche's release notes that in the 1980s it sold a special 930 Turbo with redesigned front fenders and pop-up headlights, built through the same individualization program, and 948 were sold between 1982 and 1989. The look came from the 935 race car, which won the World Championship for Makes four years in a row.

The specific target here is the 935/78, the long-tailed Martini car everyone calls Moby Dick. Grant Larson, the now-retired Porsche designer who also drew the modern 935 clubsport unveiled at Rennsport Reunion VI in 2018, designed the Flachbau RS. In Porsche's release, Larson calls it "a modern, fitting reinterpretation of the iconic 935 design."

What changed on the body

The front fenders sit lower and carry slatted louvers that vent the wheel arches and cut pressure inside them. The new fender shape meant Porsche had to rework the fuel filler flap and its mechanism, and the front bumper is all new, with Manthey canards on its corners.

The round 911 headlights are gone. In their place are three slim LED units stacked in tiers for high beam, low beam and running lights. Porsche says the low and high beams are each just under 1.5 inches tall, and the running lights are under 0.78 inches.

The paint is Grand Prix White, a 911 color since 1974, matched for this car against a historic white 911 from the Porsche collection. Matte black sections and exposed carbon add contrast, and the U-shaped element on the hood echoes a graphic from the Martini 935/78. Carbon aero discs cover the rear wheels.

A bigger wing, tested hard

Out back is a new wing on S-shaped mounts, inspired by the 992 911 GT3 R race car but almost two inches higher. It adjusts by hand to three positions, and Porsche says the adjustment and its markings are protected by patent. Working with the Manthey Kit's splitter, underbody and diffuser, the wing makes about 1,221 pounds of rear downforce at roughly 211 mph in its High Downforce setting, according to Porsche, which is two to three percent more rear downforce than a GT2 RS with the Manthey Kit in comparable settings.

Testing went well beyond a typical custom job. Porsche ran crash and airbag simulations, structural analysis of the wing loads and CFD work before any tooling was approved. Then it built three test vehicles, put the wing on a hydropulse rig, and ran them in lighting and wind tunnels, on the Mendig airfield and for 50 laps of the Nordschleife. Porsche says the testing simulated about 93,200 miles of customer use on the wing.

"The Flachbau RS remains extremely stable and precise even at very high speeds," Porsche test driver Lars Kern said in the release. When a camouflaged test car lapped the Nürburgring, Porsche notes, video hit social media almost immediately.

Lighter, and stripped behind the seats

The powertrain was left alone in agreement with the customer. Alexander Fabig, Porsche's vice president of product offering and individualization, said in the release that the conversion was still "very challenging," and that the goal was to reinterpret the 935 look without compromising safety, technology or road legality.

Weight still came out, almost 70 pounds by Porsche's count, from a car that was already about as light as Porsche could make it. The PCM infotainment system and every part of the audio system are gone, replaced by a leather-trimmed storage bin. Most sound deadening and carpet are gone too. From the seats forward the cabin keeps the original red Alcantara, black leather and carbon. Behind the seats it is pure race car, with exposed metal painted Grand Prix White and a newly laid wiring harness left visible under protective sleeving.

Flachbau RS lettering is stitched into the carbon bucket seat headrests with an outline of the Nordschleife, and a gold Sonderwunsch badge on the passenger side dash reads Werksunikat 2026, German for factory one-off. Even the road-legal stuff got the race treatment: the warning triangle and tow eye live in a removable box so they can come out for track days.

Why it matters

Porsche debuted the car at Monterey Car Week, and it is easy to read it as a rich owner's toy. It is also a statement about what the factory is willing to do now. Plenty of shops build backdated or slant nose 911s. Very few can retest an aero package to factory standards and keep the car road legal in Europe. The customer got a Moby Dick for the street, and Porsche got to show that Sonderwunsch can do more than paint and leather.