I had a similar problem with a high rear wing placement in 1974 on the Pollution Packer Bonneville with Vern Anderson driving at Bonneville. Approaching 300 miles per hour the steering became light and the car began yawing. After that, the down force was supplied via mid chassis location of the wings for down force. Gerard Brennan drove the car for Tony Fox at several events before the project was abandoned. The high rearward placement of the wing in 1974 resulted in a moment about the rear axle lifting the front wheels. A small wing over the front axle did not compensate sufficiently. Probably not a wise decision to try to solve one aero problem with a counter-aero solution. Proper aero design is easier now with CAD software. The Silver Arrows didn't have that technical aid, either, although you would think their wind tunnel testing could have exposed the problem.
