The nylon screws appear to be tightened down on the corners to keep it in place and presumably remove tension from the cables. Just guessing on that part.
If you look carefully, you can see them just below the wheels in this photo:
http://www.guidetothepoint.com/thepoint/gallery/img.asp?img=cp98ptvehicle.jpg -------------
Jeff
Webmaster/Guide to The Point
Millennium Force laps: 50