Westfall mounted a cooling radiator ahead of the engine as in an automobile, cutting a hole through to allow a propeller shaft.
After replacing the Sport's Ford Model A engine and modified OX-5 radiator with an air-cooled 65-hp LeBlond radial, Westfall logged 1000 hours flying air tours across the United States.
Just before the war began, the US Civil Aeronautics Administration mounted a crackdown against homebuilt aircraft, and Westfall was sent to jail for several months as an example to other experimenters.
[2] By 1964 Westfall desired a two-place airplane, and began designing a negative-stagger biplane which he named the Mark V Special, a loose reinterpretation of the Beechcraft Model 17 Staggerwing.
It had steel-tube fabric-covered fuselage and wood wings, a streamlined windscreen and Cessna-type spring main landing gear.
[1] The aerodynamics resulting from this arrangement were analyzed by William H Durand in a series of articles in EAA's Sport Aviation magazine.