In answer to Sheridan Thynne’s (January 2000) query asking for any more examples of two different circuit configurations being used during one event. While no other Grand Prix has had this happen, it has occurred during a World Sports Car round.
The 1957 Buenos Aires 1000km race was held at the Circuito de la Costanera Norte, the shape of which was similar to the AVUS circuit, but with flat hairpins. After the first practice the circuit was considered unsafe and a chicane was added on the main straight to slow down the cars.
I am, yours, etc.,
David Smith, Studley, Warwickshire