I had always had longer hair then the typical male, when I decided to start growing it out about two years ago, I went in and just told them that I was going to grow my hair out long and if you could cut it so it would be shaped right. They asked how long? I told them I eventually wanted to go past my shoulder, they said ok and the deed was done. I still present in boy mode and I now have hair at my shoulder, if you ill it back into a low pony tail most people don't give it a second thought. I do randomly get mam'd in boy mode, but I'm also shaving really close and have been on HRT for a several months so I just roll with it. Any way, it's not that uncommon to have long hair as a guy anymore so I really wouldn't see much issue with you growing it out.