Expanding on Menno’s method, this gets you pretty close:
Extend cross centers out to 120 guide circle
CPlane to Stbd
Poroject cross hairs to Surf
3-pt Cplane using Fore/Aft Cross at surface for pt 1 and 2 and vertical cross at top for 3rd pt to get a good average for the CPlane
Move the CPlane to the cross centre on surf
Draw 60r circle from the new CPlane 0,0,0
Project circle onto surf
It is a pretty wavy surface so if you wanted a better result, you could fill the circle (2nd last step) with a planar surface and rotate it and the circle around until it looks best, then redo the CPlane to that new position before projecting
