During World War II car-styling work was scarce and Frua had to turn to designing children's cars, electric ovens and kitchen units, as well as a monocoque motorscooter.
Frua planned for post-war times: in 1944 he bought a bombed-out factory, hired 15 workers (including Sergio Coggiola, who founded his own carrozzeria in 1966) and equipped himself to design and build cars.
After Ghia-Aigle finished coachbuilding, a former employee, Adriano Guglielmetti, started his own business and founded Carrosserie Italsuisse in Geneva.
He followed each car's realization to the last detail of fully functional one-offs and prototypes, often driving them to their presentation at the motor shows in Europe.
In 1963, at the age of 50 and at the peak of his career, Frua designed a range of cars for Glas, Germany's smallest car-maker.
Although he was not the principal designer, Frua produced the bodywork and did final assembly and detailing for Peter Kalikow's Momo Mirage prototypes in the early 1970s.
In the 1970s Frua reduced the frequency of his presentations, but in the sixth decade of his life he still demonstrated his good taste and craftsmanship to the younger ones who already had taken their role in the industrial process.
There was no longer a demand to build completely detailed and functional prototypes in less than ten weeks, and no more customers for special bodied one-offs.
One of his last designs to enter series production was the two-door GT Maserati Kyalami first shown at the 1976 Geneva Motor Show.