It seems to me that the most successful transgurls are really, really skinny. Like 30 pounds below "normal" weight. This gives them bodies that are pretty close to genuine girl models: tall, with narrow shoulders and narrow arms. The next most successful transgurls are those with quite a bit of extra weight on them. These gurls have lots of padding around, and can manage to look soft and feminine. And most can get some serious cleavage rocking, too.
No, I don't fall into either of the above categories. I'm fairly lean, but it's muscular lean, not skinny lean. Which does not work at all.