This is a big point often overlooked. Generally, the Mark V frame has a shorter head tube than comparable frames of similar top tube. Also, it only has a 5cm drop which makes the head tube effectively shorter since your seat height is set with regards to the BB. And a lower front end makes the top tube even longer.

I just (this weekend) built up my Mark V. I (6'1", 34" inseam) was on the fence between a 59 and 62. My conversion had a 58cm top tube so I was dead in between sizes. I went with the 62 due to head tube height (and the $50 off for a '07 teardrop tube frame). After my initial test ride, I'm glad I did. With about 18cm of spacers and an 84* stem, I've got about 1"-2" of seat to handlebar drop which I find about perfect.

Oh, I run drop bars if that helps.