IME keeping multiple male flashers is the way to go. Their color intensifies and they display throughout the day. I would go for 3 or more, as they set up a hierarchy. If you only got 2 one would chase the other. Multiple specimens keeps the dominant male busy displaying his dominance.
If you look through the threads about flashers you will find a lot of people keeping multiple males whether same species or different. I currently have a mckoskers, a lineopunctatus, and 2 flavianalis in the same tank and they are fine.