For a hard launch, you want to get as much power to the ground as possible in the shortest period of time. In the 335, rev to ~2k in 1st and let the clutch out more abruptly than usual. Don't dump it, but let it out quick so you aren't slipping it. Tires shouldn't complain too much, maybe a chirp.
You may not win a drag race with that method, but it's a safe way to launch the car quickly with minimal stress on the drivetrain.
If you're going to turn DSC and DTC off ..... do it on a wiiiide open area, like an empty parking lot. You are on your own when you do that (BE CAREFUL). I would just turn DTC off to start with (one press). It will allow the tires to spin but not allow much side-to-side behavior (e.g. drifting).
6K is the right shift point as noted.
Launching in 2nd will put more stress on the drivetrain.
And please again be careful.
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