Ok, the geometry on the IRO's is driving me goofey. I'm looking at spending my tax refund on another bike and I believe a Mark V Pro is in my future. However I have no idea what size to buy. Traditionally, a 56 is too big for me. 54 / 55 seems spot on. Is the 53 going to be too small? I really don't like long top tubes and everyone says IRO's run small. I am 5'11 with a 31" inseam.

thanks in advance..