I'm 5'11" with a 32-34 inseam for pants, the bike I have is a 54 in a Vilano and they went even with frame sizes from 50-60 if I recall. I find the step over for the 54 is right about as tall as I'd like it to be even with a Pake top tube pad that recently bought for it. Mine has a sloping top tube that I occasionally scuffed with my sneakers after riding for an hour or so prior to the top tube pad. Flat footed and it's not an issue with any dangling appendages in the crotch area. If you've been on a 60 and had no problems with that, then a 57 shouldn't be an issue. What your inseam for pants that you wear vs actual crotch to ground clearance with your riding shoes of choice might determine what you would prefer. If it's not too late you might be able to email customer service and change your order to a 55 ? It takes them a day to sort out that anyway before most places fill the oder and ship later in the afternoon ? Just me personally, but I'd rather extend the seat tube to fit rather than have a lot of excess to grow into that is unused. But that means you're probably at the max height you could ever resale the bike to another ?