You are not going to like this answer but - your mileage may vary. You might never know how susceptible Your body will be towards estradiol so... Given that You admit that Your starting point is not very feminine and You absolutely do not in tend to start extensive weight loss programme, then that might buy You some time. If You do not proceed with other explicit and visual indicators, like plucking out eyebrows to the extend when they are unmistakably female, wearing make-up everywhere etc - then only boobies might be the ones which could betray You. As for me - I am 35 now - and I dont know how much time I have left. I have heard that 5th month is sort of major landmark after which everything just spirals up... At the moment, I am often being asked to reveal my secret how I suddenly look 5-10 years younger and how I managed to loose a lot of weight fast. One friend of mine got an idea that I might be having cancer, because I keep loosing weight, falling out of cloth sizes and my face suddenly looks narrower. I sometimes get confused looks from complete strangers, but honestly, I do not make much effort to pass as a male - I am somewhere in the androgynous style now. So, people do notice, but most probably they wont get an idea what is going on. As long as You can provide decent explanations - You should be able to pull this off.. plus, those who see You everyday are the ones which are the least likely to see Your changes.