[Richard]

The FSA S9/C10 rings were engineered when Campy's 10 speed chain was 6.2mm wide. Campy realized the error of their ways and came out with the Ultra at 5.9mm, close to the Shimano at about 6.0mm.

You should be able to run any of the current 10 speed chains with those rings. It's my understanding that the difference is not the thickness of the rings but the spacing between the rings.

It's similar to when Shimano came out with 9 speed and advised those upgrading from 8s to change the inner ring to the 9s which narrowed the space so as to improve shifting and prevent the narrower chain from wedging between the rings. But I've never seen that happen and know lots of people who simply used their 8s cranks when switching to 9s with no problem.