I bought an Infinito CV earlier this year and has a similar issue. I normally ride a 56cm, but the size run was 55cm and 57cm. After riding both, I chose the 57 and went with a slightly shorter stem than stock and running about 1mm of spacers. The benefit is that the bike is more stable and the front end feels stiffer die to the shorter stem and minimal spacers.

Also, not sure if the Oltre 3 has the same seatpost as the infinito, but if it does, there is a lot of adjustability fore and aft.

Good luck with the choice