I'm a hair under 5'10" and just built up the 59cm and it fits right. I called Tony and he personally gave me his word that the 59cm is correct for me. It sounds big but if fits more like a 56cm/57cm in other frames. The 59cm is from the BB to the TOP of the seat tube. To the center it's 55cm. Call Tony for definitive advise.

The 56cm will technically work. You can get it to fit. But will it be ideal?

I also really dislike riser stems and with the right size frame, I can run a flat stem (with some spacers).