Hi Tom,
Have you ever used the Sunray FZ-12 coil for the CZ-3D? Can more depth really be expected from the 3D with this 12.5" coil over the Fisher 10.5" coil?
I have found the CZ 10.5" coil to give nearly identical performance to 12.5" Sunray coil .... in depth capabilities & soil volume coverage. Does not matter which CZ platform.