In 1952, he left Boisavia and joined Robert Denize where he designed the CP20, which looked like a miniature Spitfire - its wing shape especially.
The Scintex company was established in 1956 by Jean-Michel Vernhes and set up a production line to make Emeraudes, by now in great demand from French flying clubs and private owners.
In 1959, Piel moved to Scintex and the following year they developed the CP301C variant, which had a sliding canopy instead of the upward-opening doors of the earlier model.
Piel later moved to CAARP (Cooperatives des Ateliers Aéronautiques de la Region Parisienne).
In 1965, CAARP was set up by Auguste Mudry, principally as a design bureau using the skills of Piel, Nenad Hrissatovic and Louis de Goncourt.