The next step was the design of a fighter with full operational equipment. A further increase in power was needed to meet the operational requirements, and the resulting S.A.I. 207 used a 750 h.p. Isotta-Fraschini Delta R.CAO inverted-vee engine. Aside from the engine change, and the fitting of a three-bladed airscrew, the main difference between the two fighters was the mounting of armament to the later model. The S.A.I. 207 carried two 20-mm. Mauser MG 151 cannon and two Breda-SAFAT 12.7-mm. machine guns. After tests, in which the fighter achieved 398 m.p.h. in level flight and nearly 600 m.p.h. in dives, 2000 examples were ordered by the Italian Air Ministry. However, only thirteen were actually built, the remainder of the contract being diverted to the final development, the S.A.I. 403. Three S.A.I. 207's equipped the 3° Stormo C.T. at Ciampino and Cerveteri in July, 1943.
Dimensions of the S.A.I. 207 were: span 29 ft. 6 1/2 in., length 26 ft. 3 3/4 in., height 9 ft. 5 in., and wing area 149.6 sq. ft. Empty and loaded weights were 3858 and 5324 lb. respectively. Performance included a cruising speed of 304 m.p.h., a range of 528 miles, and a service ceiling of 39,370 H. Climbing to 19,680 ft. required 7 min. 33 sec.