I think you will have a hard time finding the kind of water you are describing in St. Louis. There's a guy in St. Louis that seems to know the secret formula to catching carp: http://missouriflies.com/
I've been focusing on carp in St. Louis for a year without much luck. A lot of the carp I find are the Asian carp, which I hear won't take a fly. Finding common and grass carp has been a little difficult but not impossible. I think we are pretty close to the carp spawn for some areas, so you may have some luck catching one then. I did catch an Asian carp last week on a creek feeding off the Meramec river; however, I didn't see it and it didn't eat my fly, so it was more blind luck than anything.