Film curls when it is dried without enough humdity. If you're using the hair dryer method, the good news is that the curl is almost _all_ lengthwise. It's curly as heck, but you can straighten that out pretty well. Just put a bunch of books and you're okay.
Side-side curl is harder. It is when you hang dry, there isn't enough humidity, _and_ you've hung it improperly from whatever hangers you are using. I use plain clothes hangers, and I have to be careful to clip just the very, very end of the film right in the middle. Then I do the same at the bottom end. If I clip too much and/or not in the middle, it starts to twist.
allan