I had 4 males in my group (one was a late developer), as they got more mature, they did get more aggressive with each other (one time saw two of them lip-locked flying around the tank). How bad this might get I cannot say, as I rehomed my 7 after the pencilfish incident. A tank with lots of line of sight barriers would probably help, but I suspect that with just two males the weaker one will suffer, I suspect that multiple males works better.