While I like automatics, I have read a little
The theoretical optimum shift point is the point at which the transmission torque (engine torque at rpm x gear ratio) in your next gear will be higher than the transmission torque in your current gear.
Just like the NSX, the wonderfully flat torque curve of the 370Z means that the best shift point is as close to redline as possible, which also means you can maximize your time in first gear, which is how you can beat peakier torque cars - more time in lower gears = more acceleration.