As pictured the green pen is about 36" radius, O 72, the module is 4' X 4'. Inside radius is 4 1/4" less 31 3/4" O63 1/2.
The piece, laying free, not installed, is pre-bent by hand, note that there is a good bit of work positioning the ties. All Gargraves track pictured was used from another layout. Two DeWalt (Yellow) tools are pictured. Left is a drill/driver, with a 5/64" drill bit, to pre-drill the ties. Right is an impact drive, with a #1 bit to install Atlas track screws. As the track is bent, the ends are adjusted to square at the open end before the next piece is installed. It takes a lot of screws.