Frank Costin designed dozens of cars, as well as boats, airplanes, ultralight aircraft, bobsleighs and the dipper arm for a JCB digger. And he is the COS in Marcos!

Costin was an engineer with the de Havilland Aircraft Company when, in 1954, his brother Mike, a former de Havilland engineer then working for Lotus Engineering Ltd., asked him to design an aerodynamic body for a new racing car. Intrigued by the idea of applying aerodynamics to racing cars, Costin designed the body for the Lotus Mark VIII

 Unlike his brother, Costin was never a Lotus employee; his work there was either as a paid consultant or as a volunteer.

In 1956, Chapman was commissioned by Tony Vandervell to design a Grand Prix racing car to challenge Maserati and Ferrari dominance of the formula, Chapman recommended Costin to Vandervell as the body designer. Costin designed the body for the Vanwall that won the first Grand Prix Constructors' Championship.

Later, Costin was also involved in a number of road car projects for various manufacturers including Lister and Lotus, where he contributed to the early aerodynamic designs; Marcos, which he co-founded with Jem Marsh (MARsh and COStin); and racecar chassis for Maserati, Lotus, and DTV.

He also created an ultra-light glider with Keith Duckworth, an old friend and his brother's business partner.

Chapman approached Lotus number eleven, determined that he and aerodynamicist Frank Costin — who had brought science to the art of Lotus panel design — would pencil the proposal on clean sheets of paper.

Not only was the resulting car smaller and lighter, it had the spectacular look of a winner — and it was a formidable competitor, taking the checkered flag almost 150 times in 1956 alone, its first year on campaign. This included a win at Le Mans in the 1100cc class and a seventh overall, only 27 laps behind a powerful D-Type Jaguar.

The Lotus Eleven is still the most successful track car in Lotus history.

The relationship with Chapman ended when Frank decided that being paid was a good idea and became a freelance (his remuneration for five years' work for Lotus was a Ford Anglia).

https://www.motorsportmagazine.com/archive/article/september-1984/35/cars-frank-costin

Thanks Steve!