Ridgerunner, the problem is that both trees are commmonly called ironwood, and Carpinus caroliniana has about a dozen other common names. Around here, we call Carpinus ironwood, it is listed in 90% of field guides and books as American Hornbeam, but the common name in most areas isn't hornbeam. It commonly goes by blue beech or musclewood in a lot of areas. Ostrya is listed in 99.9% of books as hophornbeam, but is usually called ironwood in the areas it grows. Around here, hophornbeam is so uncommon that most local people don't have a common name for it. I've only found it in scattered local areas with basic bedrock/soil, and it's usually small and twisted. So like you said, when you get one book that lists the trees opposite of what most of them do, it only adds to the confusion.