Absolutely. One should never let the bars dictate where you sit on the bike. The proper seated position is first and foremost in the fit process. Everything else follows from that.
But I look at your bike, and your height (and inseam) and wonder... Not much post showing, he might be better off with longer cranks and a smaller frame....
I mean, You are 6'1 and ride a 61. I am 6.25 (realistically, I always round off to 6'3") and prefer the tighter frame, more post and in some cases a longer crank. Your inseam is way too long for 175's I'd think.
But if it feels right, it is right. I know you changed out that crazy -17° stem at one point, (though they do look good on traditional geometry).
So, now I'm really curious. My saddle height is 810mm measured to a straight edge across the top, dead level. It's a pretty flat saddle, but has maybe a 4mm "dip" from the straight edge so some might say the saddle height is actually 806mm. I always use a straight edge and measure to that to be consistent. I arrived at that saddle height over years of trial and error and not by any formula. I have 95mm of setback at that height. I run a 130mm stem and rotundo bars on that bike which have a reach of 83mm. @carbonLord...your Ergosums have a 89mm reach and you run a 110mm stem. I bend and land right on the bar hoods which are about 77-78cm from the tip of my saddle to the nearest edge of the hoods. Feels really good and a natural place to land. No unnatural reaching at all. If I thought for a moment the bars were either pulling my natural seated position forward or pushing me back I would change them immediately. I never build a bike or spec a frame without knowing what bars and stem I will be using. Differences in bar reach etc can have even more of an effect on fit than an incremental change in frame size, all else equal. When I tried the -17 degree stem, I was experimenting a bit for aesthetic reasons, knowing full well what range of steertube etc I was playing with. I used that first because if it didn't work out (which it didn't) I could cut some more steertube and go to a -6 degree stem but I couldn't do that in the reverse order. None of that process was not ridiculously thought out before I started. Initially I thought a 120mm stem would be ok, but in the end found that the 130mm was perfect for me.
So I struggle to understand how you can have such a problem with your fit and insist the bars are forcing you forward. Easy fix, change them. Yet, sounds like you are even taller than me on a smaller frame, not that means much without knowing all the other physical attributes. However, like you say, if it feels right, it is right. So be it.
But I've totally missed your logic as to suggesting that due to my height and inseam that I should perhaps have 1) a smaller frame; and 2) that my inseam of 91cm is way too long for 175mm cranks.
A smaller frame does not change my seat height. I'm a bigger guy (not a waiflike pro with nothing but bone above the wasteline). So when I'm in the drops that puts more weight forward on the bike and I would argue that a 61 Colnago puts me in a very balanced position. Good weight over the front so that it's not feeling like it's 'washing out" and far enough back that I can confidently descend without feeling like I'm one small mistake away from going over the bars. A pro who weighs 160lbs at the same height might very well have a shorter (lengthwise) frame as his center of gravity is naturally going to be further back in the same postion. There is nothing worse than center of gravity which is too forward while descending (imagine riding in a tt position on a short wheelbase). For me, this frame feels like my ultimate sweet spot. If you're a bigger guy weight wise, and ride in the drops aggressively, a little bit longer frame "might" serve you well. Don't flame me because I said that, I just wish more people would consider what's "right for them" versus adopting what I call the "woman in a shoe store mentality".
But back to your theory on crank length... again out of curiosity what crank length would you put me on, if not 175mm? And how do you arrive at that number?
Thanks for listening, or not, if you didn't. I generally try to stay way clear of fit issues on the internet, but I think this is generic enough that I'm ok. Oh, and one last thing... just because it's a Colnago, doesn't necessarily means it fits everyone. We all have our preferred geometries, and if we don't, then welcome to the lifelong process of discovering it. There's lots of great bikes out there.