So, I hadn't really run Stadium much, just once with every other track to get a baseline time and all; get something on the board. But I finally went in and took a look at the bridge. Seemed enticing to find a way to jump off it for a shortcut, and well, it's SUPER easy to do that, problem is, the laps no longer count, so not valid, until that's rectified. Here's a demonstration of it, taking the course to a hypothetical sub 3.

I did try going backwards alittle bit, then forwards to see if that'll fix it, but no luck. Didn't try it out for too long, so will likely come back to this, but if anyone has any ideas/discoveries I'm happy to hear them. :)

You can also get up the bridge from below by dashing off the course on the side with the boost panel and trying to hit the base of the bridge. Coming close is good enough.