Stipa later became convinced that German rocket and jet technology (especially the V-1 flying bomb) was using his patented invention without giving proper credit, although his ducted fan design had little mechanically in common with turbojet engines and nothing at all with the pulsejet used on the V-1.

Stipa spent years studying the idea mathematically while working in the Engineering Division of the Italian Ministry of Air Force, eventually determining that the venturi tube's inner surface needed to be shaped like an airfoil in order to achieve the greatest efficiency.

Initial testing showed that the intubed propeller design did increase the engine's efficiency as Stipa had calculated, and the additional lift provided by the airfoil shape of the interior of the duct itself allowed a very low landing speed of only 68 km/h (42 mph) and assisted the Stipa-Caproni in achieving a higher rate of climb than other aircraft with similar power and wing loading.

Unfortunately, the intubed propeller design also induced so much aerodynamic drag that the benefits in engine efficiency were cancelled out, and the aircraft's top speed proved to be only 131 km/h (81 mph).

Stipa himself never had intended his intubed propeller to be employed on single-engine aircraft like the Caproni-Stipa — which he viewed merely as a testbed — instead envisioning its use in large, multi-engine flying wing aircraft he had been designing in which the aerodynamic drag properties would not be significant, and the Italian government publicized the Stipa-Caproni's design as an example of Italian aviation technology prowess.

None of Stipa's flying-wing aircraft designs were built, but experiences collected with the Stipa-Caproni did become an important influence in the development of the motorjet-powered Caproni Campini N.1.

[2] In Australia, Lynette Zuccoli and Aerotec Queensland designed a 3/5-scale replica of the Stipa-Caproni, accurate even in terms of paint scheme and markings, powered by an Italian Simonini racing engine.