I can't answer that question but I do know what you're talking about. I'm about 6' 1" with a normally proportioned body and I fit best on a 59cm bike. I comfortably ride that size. I also have 5 Colnago's and know all about the shorter top tubes. I like Colnago's frame geometry.

That being said, only one of my Colnago bikes has a 58cm seat tube. My other Colnago's have 60cm, 61cm, 61.5 and 62 cm seat tubes. The 60cm Colnago is my favourite and the 61cm is very rideable while the 62 cm bike is still good to ride but my stand over height is getting a little close and top tube is reducing my 'feel'.

I have played around with stem lengths and I like a stem of 120cm to 130cm on all of my bikes. Aesthetically they look best and the Colnago shorter top tube lends itself to a longer stem. I feel my body 'covers' the bike and gives me the sensation of total control of the bike as I am placed further over the front wheel.

I can imagine a 60cm seat tube would be a bit 'snug' for you and I would suggest trying a frame that is a little smaller and see how you go (you have probably tried that anyway). There are a number of bike brands that have similar geometry and ride characteristics as a Colnago such as Olmo and Pinarello.