One piece GT-500 rotors on my car. Floating two piece is actually a counter to knockback. Which is why captdistraction is moving that direction.
I drive the car on the street as well, but the issue is only really present on the track. 315 section Cup 2 tires at all four corners for the track, regular old summer performance tires on the street. Something (likely multiple things combined) in there is flexing through the corners. It never seemed as bad as Terry Fair experienced, but I'm not a licensed competitor either.
Solid explanation! Thank you, now I have a justification for spending nearly 1000 on 2 piece DBA rotors!!!!