OK, here's the issue:
I've decided my current conversion is a tad too large (58 c-t st and 56 c-c tt), and so I want a new training bike. Basically, I'm considering two options. The first is to get a 53 cm IRO mark v (53 c-t st and 54 c-c tt). The second is to really deck out a univega super-ten that I already have and have been using to get groceries with for a while. At the moment it fits alright, but isn't configured for hard riding, so I can't tell how it would be as a new training bike. The super-ten measures 51 c-t st and 54 c-c tt.
Everything else aside, how much would having a 2 extra cm on the seat tube matter? I'd prefer to just use the old frame and spend the $250 I save on a brooks swallow or something.