David,
It is true that the SC carriers are limited to eight analog input SCC modules (not counting cascaded modules). However, the majority of these modules have two channels. Thus, the SC carriers do provide access to all 16 of the DAQ device's single-ended analog input channels. Below, I have included a link to the product pages for the analog input SCC modules:
Analog Input SCC ModulesGood luck with your application.
Spencer S.