Also, consider the thermal expansion.
I have a buddy whose lugs came loose on his car (not a Supra) after he added spacers because his brakes got hot on a spirited drive.
You'll be generating far more heat on a track day.
Also, I'd recommend that you go for a wider set of tires and maybe...
No experience with the G87 chassis, but the F87 chassis on Gran Turismo has a lot more body roll than I was comfortable with.
Also, this is probably ownership bias, but I preferred the power delivery of the B58 over the S58.
The Z4 gauge with its G-force meter and stuff would've been a better fit for the Supra.
I haven't met any Z4 owners who would find a g-force meter relevant to their usage of the car.
Antigravity batteries. You are lifting 40 pounds from very near the rear axle, so you are changing the balance of the car. Can't say you'll feel it in street driving, but maybe on the track it'll be more noticeable with a more front-heavy car.
In the Seattle area. It's very seasonal -- during the summer, especially when I'm in nearby Bellevue with all the tech money, a couple a week. Now that it's cold and rainy, my Supra is basically the only one I see, especially since I tend to stay closer to my place in Queen Anne.
I did an Oregon trip and did end up taking some CA roads to get from Crater Lake to my hotel on the coast road. There are some brilliant mountain roads in that area.
In other news, the damage to the car is getting fixed in January.
In the meantime, the malfunctioning parking sensor will be feeding me all sorts of interesting conspiracy theories in Morse code when the car is not moving.