Your spot looks like a blast.
Mine is mainly my back yard which is about 1 acre and the driveway and road. Unfortunatley my wife won't let me tear up the grass to make a proper track.
Have you looked into these,
http://www.novarcproducts.com/clutchshoes.html
A set of those shoes with Mugen 1.0 springs would definitely be an improvement over the fiber ones.
rolland