Domenic, if you haven't already seen it, you ought to check out this article, courtesy of pmflyfisher.
It's about the Great Lakes but has excellent info that can be applied anywhere, although fly selection may be more of a local thing. It's probably best to work on your presentation first, using any fly that is known to catch carp, and then start trying different flies until you find one that works where you are. The "wrong" fly probably won't spook them but the wrong presentation will, regardless of what fly you are using.
Try for the fish that are grubbing on the bottom, especially the ones that stay in one place for a while. They are definitely feeding and are usually so preoccupied with their search for food that they are less likely to get spooked. I even motored right past one such bottom grubber and then drifted back and caught it. I had motored practically over its head in 2 feet of water and it never left its feeding spot (until after I hooked it :hehe: ).