Beau, every time! Bo seems like something you'd yell. BO! I've known one young man named Beau, so I guess it does work as a full name. Though odd in a French-speaking community, where I live, "Hey, Handsome!" Though the young man I knew was good-looking.
Haha, yes. It would be odd here in Québec too, but we might move to BC, and I just like the sound. The long o. I may stick with Ro though for Romain or Robert.