Trying to keep really long hair, and still appear masculine, is tough if you don't have other masculine features to set it off. I know a guy who has beautiful hair that comes down to his hips. But, he's also 6'5" and has a beard.
Honestly, I think you will have more luck passing if you go with something very layered that is only about collar length, like one of these, for example:

Either that, or you can say, "Sod it, I'm keeping the hair!" and accept that it's going to take hormones to make you look masculine. Of course, a lot of it also depends on the shape of your particular face. Sorry I can't give you better advice.