The oddest and most unconventional contender - probably for any aerial competition - was the Piaggio-Pegna PC.7.
The floatplane (or should we call it a 'foilplane'?) was built for the 1929 Schneider Trophy contest. A cantilever high-wing monoplane with long slender fuselage, it had twin hydrofoils instead of floats and was intended to float with the wing resting on the surface of the water.
The PC.7, designed by Giovanni Pegna, was intended to float deep in the water, with the wings resting on the surface. The engine (723kW Isotta Fraschini Special V.6) had an extra shaft and clutch controlling a water-screw at the back. The plan was for the aircraft to first operate using the water-screw and a lower rudder - like a boat. As it gained speed, the hydrofoils would generate lift and raise the aircraft, clearing the main engine/propeller above the water. The pilot would then switch to conventional controls, and the main engine clutch would be engaged…
Without the aerodynamic drag induced by floats or the weight they added to an aircraft, Pegna projected that the P.7 would reach high speeds. Sources differ on the speeds he predicted, claiming both 580 km/h (360 mph) and 700 km/h (434.7 mph).
The PC.7 never flew. Although theoretically possible, the control/clutch configuration would have required a pilot with more than two arms. In practice, problems with the respective clutches prevented the P.c.7 from ever taking off, and although water trials were conducted on Lake Garda by Dal Molin of the Italian Schneider team, the construction of a second aircraft was abandoned.