Interesting Owlie about the WSD and unisex specs being the same. I don't really know much about all of the #'s, but I looked at the specs on trek's website, and you are correct, all of the measurements seemed to be the same between the Lexa and 2.1 in a 56. I think the 2.1 i test rode was actually a 58. I think the Lexa was an H3 fit (most relaxed) and the 2.1 is H2 (more aggressive), so that might make a difference.
If Roo is 5'9 and on a 56, do you think it is feasible that I am also comfortable on a 56 (at 5'11)?
Given that I am new to road bikes, and the position is very different, it's hard to know if it feels ok.