Are these wood stakes you are attaching the PVC to? I would be concerned with them rotting in time and then the screws will not be holding anything. Pressure treated wood will rot in time. Also if you are below ground level you will need some type of retaining wall [cribbing or rocks] to keep soil from washing on to track. I've never had good luck with the plastic edging staying in place. The Aristo 10' turnout will work in a 10' diameter circle.