The aircraft was designed to comply with the US FAR 103 Ultralight Vehicles rules, including the category's maximum empty weight of 2540NaN0. The aircraft has a standard empty weight of 2480NaN0. It features a high-wing supported by dihedral stabilizers, a single-seat, open cockpit, tricycle landing gear and a single engine in pusher configuration.
The aircraft structure is made from aluminum tubing. Its 301NaN1 span wing sits high above the pilot's seat, providing pendulum stability. The controls are very unconventional and all are canard mounted, which has two surfaces. The canard surfaces move in unison to produce pitch and separately, in opposite directions, to produce roll. The large fixed dihedral stabilizers provide yaw control as the wing has no dihedral of its own for yaw coupling. The canard surfaces are mounted to the front of the main keel tube, which serves as a fuselage. The pilot is accommodated on an open seat bolted to the same tube. The Cuyuna 430 powerplant is located behind the pilot.
In service the control system has proved inadequate and the aircraft is difficult to control in flight, particularly in air that is not smooth and there have been a number of loss-of-control accidents. The Virtual Ultralight Museum describes the aircraft as "ungainly and unstable". Reviewer Andre Cliche says of the Tomcat's handling characteristics:
Cliche recommends that Tomcats be scrapped for parts and not flown.
An improved model, the Pintail, was later introduced by Haynes, which has control surfaces on the trailing edge of the dihedral stabilizers, but it is unclear if this fully addresses the original design's deficiencies.
