Modern F1's are very sensitive to bumps, uneven surfaces and rideheight (well Interlagos and the weird new first corner at the GP-Ring show that quite well) so it would take quite some thinking, adjusting and a great driver to maximise an F1 car on that track. Then five and a half minutes don't seem unrealistic. Compared to the six minutes record that Stefan Bellof put on the clock in his Porsche 956 during qualifying in 1984, that means an improvement of about 1,5 s per km. Given the Porsche 956 potential and current F1 characteristics that should be possible ... just.
