With the jumper on you'd definitely pass to me, it would depend with just the t-shirt. Guys moobs tend to not be as firm and float around a bit if you know what I mean, which could mark yours out as not being normal moobs in real life. Try some clothes with checks or patterns on, and an open shirt or jacket. I'm a lot smaller chested, but I can get away fine with a hoodie and jacket on without binding because it's winter, and it's very rare that I can with only a t-shirt. I'd not be comfortable like that anyway.