Reply to "Any suggestions on a better way of cutting curved roadbed?"

This is my next project. I have a lot of concentric curves O-90, O-81, O-72, O-63. I plan to make a 48" long compass that I will attach to the mid-point edge of the long side of a 4 x 8 sheet of plywood with a pivot hinge. I may even, attach my jig saw to the compass at the different cutting radii. Out of each sheet, I can get a half circle of all 4 different curves.