Sounds like your FF miles are probably mostly (or all) with CP or AC?? I don't know how many miles it is for a r/t ticket to RIO, but on Continental, from anywhere in the US or Canada it is only 35k for coach.

I think that is probably one of the best deals in the CO Onepass program, if you consider the $$ prices for tickets to Rio, or other S. American cities. Good luck finding the best deal - perhaps a consolidator as suggested above.