one urinal left between would have been sufficient to give them the conservative "space" and still be close enough so you aren't shouting across the room. Standing right next to them, as said before, might have conveyed an aspect of closeness that you don't have.
Recently I was in a restaurant (Buffalo Wild Wings) where I was eating wings and drinking beer- and I timed my bathroom break with a new buddy. It was a small bathroom, and there were two urinals on opposite walls, outside of a single stall. We were the only ones in there chatting. As I finished, I turned around and left my schlong displayed for a couple seconds before buttoning up the fly of my jeans. I stared at his eyes the whole time- to see if he would take a peek.
Hell ya he did. All guys do. I think it's what's expected in a guy scene like that- and both of us are slightly drunk. It's all good.