I don't know what's your objective, do you don't want breasts because you don't like them or because you don't want to socially transition? Because it's different, I'd guess. If you want to socially transition and not having boobs or being curvaceous to an extent, then it'll make social transition much harder, if not almost impossible. There are women who are almost completely flat-chested, but they usually have a hard time and end up wearing push-ups or paddings.
Besides, if you take HRT, you'll most likely have feminization to some degree in all your body, not just face. It's impossible to monitor and choose changes, what you'll get will depend on how your body reacts to hormones. You could be one of the lucky ones who gets really busty, but in your case, unlucky since you don't want them. Or you could get minor breast development, huge hips and a very femininized face. The combinations are endless. If you really want to transition, then maybe the risk will be worth it. In the end if you're not happy with how busty you've become, you can always undergo breast reduction surgery. That could be an option for you. Most t women want breast agumentation, not reduction, but that doesn't mean you have to as well. For me, I'd really like to become very feminized face and then average to small breasts and a low Waist-To-Hip ratio, but that's me, I'm sure many feel different. And it's okay, we don't have to want all the same things.
