Developed from the S.107 lightweight single-seat fighter and featuring a similar wooden structure with monocoque fuselage, the S.207 was essentially a more powerful, productionised version of the basic design.
The second prototype was powered by the R.C.40 version of the engine rated at 750hp at 4000m. In dives the S.A.I.207 attained an indicated air speed of 466 m.p.h. at 10,000 ft. (representing a true air speed of 596 m.p.h., or Mach 0.86), and maximum level speed was 357 m.p.h., with the 750 h.p.
Armament was two synchronised 12.7mm machine guns, and a pre-series of 12 S.207s was built during March-July 1943, several of these being assigned to the 83a Squadriglia (18° Gruppo, 3° Stormo) for evaluation, and six being assigned in August 1943 to the 162a and 163a squadriglie (161° Gruppo).
One pre-series S.207 was fitted with an armament of two 20mm cannon.