You might think so, but with the downforce levels and g-force experienced in 2004, drivers complained about blackouts, and dizziness. We didn't get close to the theoretical car-levels, however, we started to see F1 closing in on what the human body can handle without help.
The Firestone Firehawk 600 is also a good read on the effect g-forces can have, that race got cancelled, but not before Paul Tracy had set the fastest with 380.896 km/h on average through the lap. While it was a bit behind the record set by Gil De Ferran the year before (388.541 km/h), they experienced more g-forces more often.