Al,
We used radial jig to draw the lines and then cut a template out of 3/4" ply and this was then use to cut 1/4" mdf. The inner loop is 120" diameter and the outer is 128".
You when you get see it in person you can all of the little goofs made with the jigsaw. And those are repeated on every base 
. We learned quite a bit from this phase of construction namely be more patient.
I now own a radial jig for my router that make 2' to 16' diameter circles.
