Nice job and probably a testimony to the driver as much as the car.
Getting my hand on a 600RWHP Zo6 once, I quickly realized that balance is more important than power. When you get more preoccupied by driving on eggshell due to high power over your racing lines your timer takes a dump. Usually high power cars make the worst drivers as they rely on the power over keeping their speed thru turns (and usually come too hot in the turn too). Kind of like a Spitfire pilot or LA7 pilot in AH, they are not the best at ACM.
as for the GT:
Did you feel that cradle lock out helps in road course too, not only drag launches? or did it stiffen your rear too much?
My GT I had didn't bounce on the rev limiter, instead it kills the engine. I found that odd, is it the same for yours? (mine's a manual).
Or that car is very well balanced or even in track mode you still have some TC/SC. I was surprised how easy it was to drift the round-abouts. You can really hang the tail with minimal control input. Do you know anything about that?
I saw a video of a GT where the tach turned red at the limiter, do you know if it's a mod? I didn't find a setting for it.