A wise old race engineer (no, not Doug Arnao) once explained to me the function of the 'fast' jounce and rebound settings of the shocks...as different from the normal (or 'slow') settings. The normal settings react to driver input (brake, turn, accelerate). The stiffer these settings are, the faster the car responds to driver-induced transients. (Too stiff and the tire can lose contact with the road.) The fast settings react to input from the road (bumps, dips, curbs)...
Kunos' Nissan GT-R GT3 @ Syracuse/Siracusa
Kunos' Nissan GT-R GT3 @ Syracuse/Siracusa