Better stick with the 56 or close to it, in my opinion. I am five foot ten inches and, though I can ride a 54cm, I prefer a 56cm for comfort sake. Height has something but not everything to do with size choice. Short torso, long legs demands a larger fit. So, too, in my case, does the rider's age. I can no longer feel comfortable on the smaller size due to a busted neck which gets awfully sore, thanks to the need to curl my neck up to allow me to see where I am going. The point is,
you need to know you and what you want the bike for.