1988, Hockenheim. German GP Free Practice. Williams tested this ultra low wing on the Fw12 Judd, basically made of just the lower flap and half-cut side panels, in attempt to reduce drag due to the nature of the circuit, back then in its original high-speed straights layout.
Also, they combined it with a lowered engine cover, with old-style-1960ish grills as air intakes instead of the classic airscoop...
They never used those solution in quali or race.
Again, they re-vitalized the same ultra low wing concept nine years later on the 1997 Fw19 Renault.
Again, just in free practice.