I contacted the author of the program and asked about the track ending. His answer follows. So I had a car make it all the way to the end of Hubski Falls, and then over the edge of the world. I don't have a picture of what that car looked like, but the batch it came from had a heavy front wheel, light back wheel, both large, skinny body with a club like head around the front axle. (See my picture and data in another comment). ---
from: Rafael Matsunaga
Hi Michael! Glad you're having fun with the cars! Yeah, the track ends somewhere between 220 and 300 meters, it's actually 300 1-meter long blocks, and due to all the crazy winding towards the end, it ends up shorter than 300 straight meters. After that, it's a free fall to death for the victorious car. :) Thanks for the link! I love seeing where people are coming from!