While I don't know the underlying mechanism here, I've discovered that, if you crash in a particular way, you can be sent forward to the next checkpoint when you respawn. Specifically, you can do this in long chains of crashes along each of the curvy bits of the track, and I believe before each of the 90° turns as well.
From my testing, I haven't gotten this to work along any of the straight sections of the track, and as far as I can tell, one of the requirements is to be facing at least slightly backwards when you crash. Some of the warps are more lenient than others, maybe depending on the specific location of the crash or your car's angle during the crash? Idk
Additionally, it feels easier to set up a warp when in the middle of a chain, as opposed to initiating one from scratch. This is why I start each of the three chains in the video with an intentional non-warp crash. The only exception is for the last two warps at the end, as the setup I use there feels very consistent.
You can opt into doing more warps than I did in the above video - you can start and end the first chain slightly sooner/later, and you can end the third chain slightly later, though those warps seem to be especially finnicky. I didn't attempt any on the final lefthand curve, though there are some that work there. The only 90° warps I opted to do were the two at the very end, as again, they seem far more consistent than the others.
I'm pretty sure that sub-6 should be doable, tho idk how difficult it would be.
