You know what, I say go for it. I'm 6'4" and I've
been riding around on a 56 with 14cm headtube for the last few months (it has a saddle to bar drop more akin to a TT rig) and it's bearable up to 50 miles. In fact the position it forces me into is damned aerodynamic so it's fast.
http://1.bp.blogspot.com/-J8iISEwX0vg/Thnmt5yaTHI/AAAAAAAAACA/NbDGb4M41aY/s1600/half-troll.png